Coupling part, photosensitive drum, process cartridge and electrophotographic image forming apparatus

ABSTRACT

A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, wherein the main assembly includes a motor, a main assembly side gear for receiving driving force from the motor, a hole defined by twisted surfaces, the hole being substantially coaxial with the gear, and a main assembly side grounding contact provided in the hole, the process cartridge includes an electrophotographic photosensitive drum; process mechanisms actable on the photosensitive drum; and a projection engageable with the twisted surfaces, the projection being provided at a longitudinal end of the photosensitive drum, wherein when the main assembly side gear rotates with the hole and projection engaged with each other, rotational driving force is transmitted from the gear to the photosensitive drum through engagement between the hole and the projection; and a cartridge side grounding contact electrically connected with the electrophotographic photosensitive drum for electrically grounding the electrophotographic photosensitive drum when the process cartridge is mounted to the main assembly of the apparatus, the cartridge side grounding contact being provided on the projection so as to be electrically connectable with the main assembly side grounding contact

The present application is a Rule 53(b) Continuation Application of U.S.application Ser. No. 09/968,657, filed Oct. 2, 2001.

Application Ser. No. 09/968,657 is a Rule 53(b) continuation applicationof application Ser. No. 08/938,893, filed Sep. 26, 1997, now U.S. Pat.No. 6,400,914. Application Ser. No. 09/968,657 also is acontinuation-in-part application of application Ser. No. 09/522,293filed Mar. 9, 2000, now U.S. Pat. No. 6,349,188, which is a divisionalapplication of application Ser. No. 09/258,314 filed Feb. 26, 1999, nowU.S. Pat. No. 6,128,454, which is a divisional application ofapplication Ser. No. 08/621,941 filed Mar. 26, 1996, now U.S. Pat. No.5,903,803.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a coupling part, a photosensitive drum,a drive transmission part, a process cartridge and anelectrophotographic image forming apparatus.

Here, the electrophotographic image forming apparatus forms an image ona recording material using an electrophotographic image formationprocess. Examples of the electrophotographic image forming apparatusinclude an electrophotographic copying machine, an electrophotographicprinter (laser beam printer, LED printer or the like), a facsimilemachine and a word processor or the like.

The process cartridge contains integrally the electrophotographicphotosensitive member and charging means, developing means or cleaningmeans, and is detachably mountable relative to a main assembly of theimage forming apparatus. It may integrally contain theelectrophotographic photosensitive member and at least one of thecharging means, the developing means and the cleaning means. As anotherexample, it may contain the electrophotographic photosensitive memberand at least the developing means.

In an electrophotographic image forming apparatus using anelectrophotographic image forming process, the process cartridge isused, which contains the electrophotographic photosensitive member andprocess means actable on said electrophotographic photosensitive member,and which is detachably mountable as a unit to a main assembly of theimage forming apparatus (process cartridge type). With this processcartridge type, maintenance of the apparatus can be carried out ineffect by the user without depending on a serviceman. Therefore, theprocess cartridge type is now widely used in electrophotographic imageforming apparatuses.

A driving system for a photosensitive member in a process cartridgetype, is disclosed in U.S. Pat. Nos. 4,829,335 and 5,023,660. U.S. Pat.Nos. 4,591,258 and 4,839,690 disclose grounding mechanism for aphotosensitive member. These are effective.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a coupling meanscapable of grounding an electrophotographic photosensitive member, andalso to provide a photosensitive drum, a process cartridge, and anelectrophotographic image forming apparatus, which comprise suchcoupling means.

Another object of the present invention is to provide a coupling meanscapable of grounding an electrophotographic photosensitive memberthrough the main assembly of an electrophotographic image formingapparatus in which the electrophotographic photosensitive memberreceives driving force through the coupling means, and also to provide aphotosensitive drum, a process cartridge, and an electrophotographicimage forming apparatus, which are compatible with such a couplingmeans.

Another object of the present invention is to provide a coupling meanscapable of grounding an electrophotographic photosensitive memberwithout deteriorating the rotational accuracy of the electrophotographicphotosensitive member, and also to provide a photosensitive drum, aprocess cartridge, and an electrophotographic image forming apparatus,which are compatible with such a coupling means.

Another object of the present invention is to provide a coupling meanscomprising a projection engageable with a twisted surface, saidprojection being provided at one of the longitudinal ends of aphotosensitive drum, wherein when a gear on the main assembly siderotates, with a hole and the projection being engaged with each other,rotational driving force is transmitted from said gear to saidphotosensitive drum through engagement between said hole and saidprojection, and also to provide a photosensitive drum, a processcartridge, and an electrophotographic image forming apparatus, which arecompatible with such a coupling means.

Another object of the present invention is to provide a coupling means,the process cartridge side of which comprises a projection provided witha ground contact which is electrically connected to the ground contacton the main assembly side to ground an electrophotographicphotosensitive member, and also to provide a photosensitive drum, aprocess cartridge, and an electrophotographic image forming apparatus,which are compatible with such a coupling means.

Another object of the present invention is to provide a coupling meanscapable of grounding an electrophotographic photosensitive drum, as wellas transmitting driving force from the apparatus main assembly side tothe process cartridge side, wherein the coupling means comprises theprocess cartridge side with a coupling recess and a ground contact, theground contact being located in the coupling recess, and the apparatusmain assembly side with a coupling projection and a ground contact, theground contact being located on the coupling projection, and when aprocess cartridge is installed in the apparatus main assembly of anelectrophotographic image forming apparatus, the coupling recess isengaged with the coupling projection, whereby the ground contact on theprocess cartridge side is placed in contact with the ground contact onthe apparatus main assembly side to ground the electrophotographicphotosensitive drum, and also to provide a photosensitive drum, aprocess cartridge, and an electrophotographic image forming apparatus,which are compatible with such a coupling means.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section of an electrophotographic image formingapparatus.

FIG. 2 is an external perspective view of the apparatus illustrated inFIG. 1.

FIG. 3 is a cross-section of a process cartridge.

FIG. 4 is an external perspective view of the process cartridgeillustrated in FIG. 3, as seen from the top right direction.

FIG. 5 is the right-hand side view of the process cartridge illustratedin FIG. 3.

FIG. 6 is the left-hand side view of the process cartridge illustratedin FIG. 3.

FIG. 7 is an external perspective view of the process cartridgeillustrated in FIG. 3, as seen from the top left direction.

FIG. 8 is an external perspective view of the bottom left side of theprocess cartridge illustrated in FIG. 3.

FIG. 9 is an external perspective view of the process cartridgeaccommodating portion of the main assembly of the apparatus illustratedin FIG. 1.

FIG. 10 is an external perspective view of the process cartridgeaccommodating portion of the main assembly of the apparatus illustratedin FIG. 1.

FIG. 11 is a vertical section of a photosensitive drum and a drivingmechanism for driving the photosensitive drum.

FIG. 12 is a perspective view of a cleaning unit.

FIG. 13 is a perspective view of an image developing unit.

FIG. 14 is a partially exploded perspective view of an image developingunit.

FIG. 15 is a partially exploded perspective view of a gear holding frameportion of the image developing chamber frame, and the gears which drivethe image developing unit, depicting the back side of thereof.

FIG. 16 is a side view of the image developing unit inclusive of thetoner chamber frame and the image developing chamber frame.

FIG. 17 is a plan view of the gear holding frame portion illustrated inFIG. 15, as seen from the inside of the image developing unit.

FIG. 18 is a perspective view of an image developing roller bearing box.

FIG. 19 is a perspective view of the image developing chamber frame.

FIG. 20 is a perspective view of the toner chamber frame.

FIG. 21 is a perspective view of the toner chamber frame.

FIG. 22A is a vertical section of the toner sealing portion illustratedin FIG. 21. FIG. 22B is a detailed view thereof.

FIG. 23 is a vertical section of the structure which supports thephotosensitive drum charging roller.

FIG. 24 is a schematic section of the driving system for the mainassembly of the apparatus illustrated in FIG. 1.

FIG. 25 is a perspective view of a coupling provided on the apparatusmain assembly side, and a coupling provided on the process cartridgeside.

FIG. 26 is a perspective view of the coupling provided on the apparatusmain assembly side, and the coupling provided on the process cartridgeside.

FIG. 27 is a section of the structure which links the lid of theapparatus main assembly, and the coupling portion of the apparatus mainassembly.

FIG. 28 is a front view of the indented coupling shaft and theadjacencies thereof as seen while the process cartridge in the apparatusmain assembly is driven.

FIG. 29 is a front view of the indented coupling shaft and itsadjacencies as seen while the process cartridge in the apparatus mainassembly is driven.

FIG. 30A is a vertical view of the process cartridge in the apparatusmain assembly and the adjacencies thereof, depicting the positionalrelationship among the electrical contacts as seen while the processcartridge is installed into, or removed from, the apparatus mainassembly. FIG. 30B is a detailed view thereof.

FIG. 31 is a side view of a compression type coil spring and its mount.

FIG. 32 is a vertical section of the joint between the drum chamberframe and the image developing chamber frame.

FIG. 33 is a perspective view of the longitudinal end portion of theprocess cartridge, depicting how the photosensitive drum is mounted inthe cleaning chamber frame.

FIG. 34 is a vertical section of the drum bearing portion.

FIG. 35 is a side view of the drum bearing portion, depicting thecontour thereof.

FIG. 36 is an exploded section of the drum bearing portion in one of theembodiments of the present invention.

FIG. 37 is an exploded schematic view of the drum bearing portion.

FIG. 38 is a plan view of the process cartridge, depicting therelationship among the various thrust generated in the cartridge, interms of direction and magnitude.

FIG. 39 is a perspective view of the opening and its adjacencies of thetoner chamber frame, in one of the embodiments of the present invention.

FIG. 40 (a) is a cross section of a projection and a recess and FIG. 40(b) depicts the state of engagement between the projection and therecess.

FIG. 41 is a lengthwise section of the ground contact on thephotosensitive drum side.

FIG. 42 is a frontal elevation of a grounding plate.

FIG. 43 is a perspective view of the coupling means with groundingcontacts.

FIG. 44 is a lengthwise section of a photosensitive drum and theadjacencies thereof, depicting the structure which is capable ofgrounding a photosensitive member, as well as supporting it.

FIG. 45 is a perspective view of the coupling means with groundcontacts.

FIG. 46 is a lengthwise section of the ground contact on thephotosensitive drum side.

FIG. 47 is a lengthwise section of a photosensitive drum and theadjacencies thereof, depicting the ground contact of a photosensitivedrum supported by a photosensitive drum shaft which penetrates throughthe entire length of the photosensitive drum.

FIG. 48 is a lengthwise section of a photosensitive drum and theadjacencies thereof, depicting the ground contact of a photosensitivedrum supported by a photosensitive drum shaft which penetrates throughthe entire length of the photosensitive drum.

FIG. 49 is a lengthwise section of a photosensitive drum and theadjacencies thereof, depicting the ground contact of a photosensitivedrum supported by a photosensitive drum shaft which penetrates throughthe entire length of the photosensitive drum.

FIG. 50 is a lengthwise section of a photosensitive drum and theadjacencies thereof, depicting the structure which is capable ofgrounding a photosensitive drum, as well as supporting it.

FIG. 51 is a lengthwise section of the coupling means, depicting thegrounding path for a photosensitive drum.

FIG. 52 is a perspective view of the drum side of the coupling means,that is, the male side.

FIG. 53 is a perspective view of the projection in another embodiment ofthe present invention.

FIG. 54 is a perspective view of the projection in another embodiment ofthe present invention.

FIG. 55 is a lengthwise section of a photosensitive drum and theadjacencies thereof, depicting the grounding path for the photosensitivedrum.

FIG. 56A is a lengthwise section of the driven end of a photosensitivedrum; FIG. 56B, a perspective view of the inward side of the couplerportion of a drum flange; and FIG. 56C, is a perspective view of theoutward side of the coupler portion of the same drum flange.

FIG. 57 is an elevation of a grounding plate and the adjacencies thereofdepicted in FIG. 55, as seen from the right-hand side of FIG. 55, thatis, the direction parallel to the photosensitive drum shaft.

FIG. 58 is an enlarged schematic view of a portion of FIG. 56A.

FIG. 59 is a schematic view of the portion illustrated in FIG. 58, asseen from the direction parallel to the photosensitive drum shaft.

FIG. 60 is a lengthwise section of a photosensitive drum and theadjacencies thereof, depicting a modified version of the grounding pathstructure for the photosensitive member illustrated in FIG. 54.

FIG. 61 is a lengthwise section of a photosensitive drum and theadjacencies thereof, depicting another modified version of the structurewhich is capable of grounding a photosensitive member, as well assupporting it.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the embodiments of the present invention will be describedwith reference to the drawings.

Next, desirable embodiments of the present invention will be described.In the following description, the “widthwise” direction of a processcartridge B means the direction in which the process cartridge B isinstalled into, or removed from, the main assembly of an image formingapparatus, and coincides with the direction in which a recording mediumis conveyed. The “lengthwise” direction of the process cartridge B meansa direction which is intersectional with (substantially perpendicularto) the direction in which the process cartridge B is installed into, orremoved from, the main assembly 14. The lengthwise direction is parallelto the surface of the recording medium, and intersectional with(substantially perpendicular to) the direction in which the recordingmedium is conveyed. Further, the “left” or right” means the left orright relative to the direction in which the recording medium isconveyed, as seen from above.

FIG. 1 is an electrophotographic image forming apparatus (laser beamprinter) which embodies the present invention, depicting the generalstructure thereof; FIG. 2, an external perspective thereof; and FIGS.3-8 are drawings of process cartridges which embody the presentinvention. More specifically, FIG. 3 is a cross-section of a processcartridge; FIG. 4, an external perspective view of the processcartridge; FIG. 5, a right-hand side view of the process cartridge; FIG.6, a left-hand side view of the process cartridge; FIG. 7, a perspectiveview of the process cartridge as seen from the top left direction; andFIG. 8 is a perspective view of the process cartridge as seen from thebottom left direction. In the following description, the “top” surfaceof the process cartridge B means the surface which faces upward when theprocess cartridge B is in the main assembly 14 of the image formingapparatus, and the “bottom” surface means the surface which facesdownward. (Electrophotographic Image Forming Apparatus A and ProcessCartridge B)

First, referring to FIGS. 1 and 2, a laser beam printer A as anelectrophotographic image forming apparatus which embodies the presentinvention will be described. FIG. 3 is a cross-section of a processcartridge which also embodies the present invention.

Referring to FIG. 1, the laser beam printer A is an apparatus whichforms an image on a recording medium (for example, recording sheet, OHPsheet, and fabric) through an electrophotographic image forming process.It forms a toner image on an electrophotographic photosensitive drum(hereinafter, photosensitive drum) in the form of a drum. Morespecifically, the photosensitive drum is charged with the use of acharging means, and a laser beam modulated with the image data of atarget image is projected from an optical means onto the chargedperipheral surface of the photosensitive drum, forming thereon a latentimage in accordance with the image data. This latent image is developedinto a toner image by a developing means. Meanwhile, a recording medium2 placed in a sheet feeding cassette 3 a is reversed and conveyed by apickup roller 3 b, a conveyer roller pairs 3 c and 3 d, and registerroller pair 3 e, in synchronism with the toner formation. Then, voltageis applied to an image transferring roller 4 as a means for transferringthe toner image formed on the photosensitive drum 7 of the processcartridge B, whereby the toner image is transferred onto the recordingmedium 2. Thereafter, the recording medium 2, onto which the toner imagehas been transferred, is conveyed to a fixing means 5 by guidingconveyer 3 f. The fixing means 5 has a driving roller 5 c, and a fixingroller 5 b containing a heater 5 a, and applies heat and pressure to therecording medium 2 as the recording medium 2 is passed through thefixing means 5, so that the image having been transferred onto therecording medium 2 is fixed to the recording medium 2. Then, therecording medium 2 is conveyed farther, and is discharged into adelivery tray 6 through a reversing path 3 j, by discharging rollerpairs 3 g, 3 h and 3 i. The delivery tray 6 is located at the top of themain assembly 14 of the image forming apparatus A. It should be notedhere that a pivotable flapper 3 k may be operated in coordination with adischarge roller pair 3 m to discharge the recording medium 2 withoutpassing it through the reversing path 3 j. The pickup roller 3 b,conveyer roller pairs 3 c and 3 d, register roller pair 3 e, guidingconveyer 3 f, discharge roller pairs 3 g, 3 h and 3 i, and dischargeroller pair 3 m constitute a conveying means 3.

Referring to FIGS. 3-8, in the process cartridge B, on the other hand,the photosensitive drum 7 with a photosensitive layer 7 e (FIG. 11) isrotated to uniformly charge its surface by applying voltage to thecharging roller 8 as a photosensitive drum charging means. Then, a laserbeam modulated with the image data is projected onto the photosensitivedrum 7 from the optical system 1 through an exposure opening 1 e,forming a latent image on the photosensitive drum 7. The thus formedlatent image is developed with the use of toner and the developing means9. More specifically, the charging roller 8 is disposed in contact withthe photosensitive drum 7 to charge the photosensitive drum 7. It isrotated by the rotation of the photosensitive drum 7. The developingmeans 9 provides the peripheral surface area (area to be developed) ofthe photosensitive drum 7 with toner so that the latent image formed onthe photosensitive drum 7 is developed. The optical system 1 comprises alaser diode 1 a, a polygon mirror 1 b, a lens 1 c, and a deflectivemirror 1 d (FIG. 1).

In the developing means 9, the toner contained in a toner container 11Ais delivered to a developing roller 9 c by the rotation of a tonerfeeding member 9 b. The developing roller 9 c contains a stationarymagnet. It is also rotated so that a layer of toner with triboelectriccharge is formed on the peripheral surface of the developing roller 9 c.The image developing area of the photosensitive drum 7 is provided withthe toner from this toner layer, the toner is transferred onto theperipheral surface of the photosensitive drum 7 in a manner to reflectthe latent image, visualizing the latent image as a toner image. Thedeveloping blade 9 d is a blade which regulates the amount of the toneradhered to the peripheral surface of the developing roller 9 c and alsotriboelectrically charges the toner. Adjacent to the developing roller 9c, a toner stirring member 9 e is rotatively disposed to circulativelystir the toner within the image developing chamber.

After the toner image formed on the photosensitive drum 7 is transferredonto the recording medium 2 by applying voltage with polarity oppositeto that of the toner image to the image transferring roller 4, theresidual toner on the photosensitive drum 7 is removed by the cleaningmeans 10. The cleaning means 10 comprises an elastic cleaning blade 10 adisposed in contact with the photosensitive drum 7, and the tonerremaining on the photosensitive drum 7 is scraped off by the elasticcleaning blade 10 a, being collected into a waste toner collector 10 b.

The process cartridge B is formed in the following manner. First, atoner chamber frame 11, which comprises a toner container (toner storingportion) 11A for storing toner, is joined with an image developingchamber frame 12 which houses the image developing means 9 such as animage developing roller 9 c, and then, a cleaning chamber frame 13, inwhich the photosensitive drum 7, the cleaning means 10 such as thecleaning blade 10 a, and the charging roller 8 are mounted, is joinedwith the preceding two frames 11 and 12 to complete the processcartridge B. The thus formed process cartridge B is removablyinstallable into the main assembly 14 of the image forming apparatus A.

The process cartridge B is provided with an exposure opening throughwhich a light beam modulated with image data is projected onto thephotosensitive drum 7, and a transfer opening 13 n through which thephotosensitive drum 7 opposes the recording medium 2. The exposureopening 1 e is a part of the cleaning chamber frame 13 and the transferopening 13 is located between the image developing chamber frame 12 andthe cleaning chamber frame 13.

Next, the structure of the housing of the process cartridge B in thisembodiment will be described.

The process cartridge in this embodiment is formed in the followingmanner. First the toner chamber frame 11 and the image developingchamber frame 12 are joined, and then, the cleaning chamber frame 13 isrotatively joined with the preceding two frames 11 and 12 to completethe housing. In this housing, the aforementioned photosensitive drum 7,charging roller 8, developing means 9, cleaning means 10, and the like,are mounted to complete the process cartridge B. The thus formed processcartridge B is removably installable into the cartridge accommodatingmeans provided in the main assembly 14 of an image forming apparatus.

(Housing Structure of Process Cartridge B)

As described above, the housing of the process cartridge B in thisembodiment is formed by joining the toner chamber frame 11, the imagedeveloping chamber frame 12, and the cleaning chamber frame 13. Next,the structure of the thus formed housing will be described.

Referring to FIGS. 3 and 20, in the toner chamber frame 11, the tonerfeeding member 9 b is rotatively mounted. In the image developingchamber frame 12, the image developing roller 9 c and the developingblade 9 d are mounted, and adjacent to the developing roller 9 c, thestirring member 9 e is rotatively mounted to circulatively stir thetoner within the image developing chamber. Referring to FIGS. 3 and 19,in the image developing chamber frame 12, a rod antenna 9 h is mounted,extending in the lengthwise direction of the developing roller 9 csubstantially in parallel to the developing roller 9 c. The tonerchamber frame 11 and the development chamber frame 12, which areequipped in the above-described manner, are welded together (in thisembodiment, by ultrasonic wave) to form a second frame which constitutesan image developing unit D (FIG. 13).

The image developing unit of the process cartridge B is provided with adrum shutter assembly 18, which covers the photosensitive drum 7 toprevent it from being exposed to light for an extended period of time orfrom coming in contact with foreign objects when or after the processcartridge B is removed from the main assembly 14 of an image formingapparatus.

Referring to FIG. 6, the drum shutter assembly 18 has a shutter cover 18a which covers or exposes the transfer opening 13 n illustrated in FIG.3, and linking members 18 b and 18 c which support the shutter cover 18a. On the upstream side relative to the direction in which the recordingmedium 2 is conveyed, one end of the right-hand side linking member 18 cis fitted in a hole 40 g of a developing means gear holder 40 as shownin FIGS. 4 and 5, and one end of the left-hand side linking member 18 cis fitted in a boss 11 h of the bottom portion 11 b of the toner chamberframe 11. The other ends of the left and right-hand linking members 18 care attached to the corresponding lengthwise ends of the shutter cover18 a, on the upstream side relative to the recording medium conveyingdirection. The linking member 18 c is made of metallic rod. Actually,the left- and right-hand linking members 18 c are connected through theshutter cover 18 a; in other words, the left- and right-hand linkingmembers 18 c are the left- and right-hand ends of a single piece linkingmember 18 c. The linking member 18 b is provided only on one lengthwiseend of the shutter cover 18 a. One end of the linking member 18 b isattached to the shutter cover 18 a, on the downstream side, relative tothe recording medium conveying direction, of the position at which thelinking member 18 c is attached to the shutter cover 18 a, and the otherend of the linking member 18 b is fitted around a dowel 12 d of theimage development chamber frame 12. The linking member 18 b is formed ofsynthetic resin.

The linking members 18 b and 18 c, which are different in length, form afour piece linkage structure in conjunction with the shutter cover 18 aand the toner chamber frame 11. As the process cartridge B is insertedinto an image forming apparatus, the portion 18 c 1 of the linkingmember 18 c, which projects away from the process cartridge B, incontact with the stationary contact member (unillustrated) provided onthe lateral wall of the cartridge accommodating space S of the mainassembly 14 of the image forming apparatus, and activates the drumshutter assembly 18 to open the shutter cover 18 a.

The drum shutter assembly 18, constituted of the shutter cover 18 a andthe linking members 18 b and 18 c, is loaded with the pressure from anunillustrated torsional coil spring fitted around a dowel 12 d. One endof the spring is anchored to the linking member 18 b, and the other endis anchored to the image developing chamber frame 12, so that thepressure is generated in the direction to cause the shutter cover 18 ato cover the transfer opening 13 n.

Referring again to FIGS. 3 and 12, the cleaning means frame 13 is fittedwith the photosensitive drum 7, the charging roller 8, and the variouscomponents of the cleaning means 10, to form a first frame as a cleaningunit C (FIG. 12).

Then, the aforementioned image developing unit D and cleaning unit C arejoined with the use of a joining member 22, in a mutually pivotablemanner, to complete the process cartridge B. More specifically,referring to FIG. 13, both lengthwise (axial direction of the developingroller 9 c) ends of the image developing chamber frame 12 are providedwith an arm portion 19, which is provided with a round hole 20 which isin parallel to the developing roller 9 c. On the other hand, a recessedportion 21 for accommodating the arm portion 19 is provided at eachlengthwise end of the cleaning chamber frame (FIG. 12). The arm portion19 is inserted in this recessed portion 21, and the joining member 22 ispressed into the mounting hole 13 e of the cleaning chamber frame 13,put through the hole 20 of the end portion of the arm portion 19, andpressed, farther, into the hole 13 e of an partitioning wall 13 t, sothat the image developing unit D and the cleaning unit C are joined tobe pivotable relative to each other about the joining member 22. Injoining the image developing unit D and the cleaning unit C, acompression type coil spring 22 a is placed between the two units, withone end of the coil spring being fitted around an unillustrated dowelerected from the base portion of the arm portion 19, and the other endbeing pressed against the top wall of the recessed portion 21 of thecleaning chamber frame 13. As a result, the image developing chamberframe 12 is pressed downward to reliably keep the developing roller 9 cpressed downward toward the photosensitive drum 7. More specifically,referring to FIG. 13, a roller 9 i having a diameter larger than that ofthe developing roller 9 c is attached to each lengthwise end of thedeveloping roller 9 c, and this roller 9 i is pressed on thephotosensitive drum 7 to maintain a predetermined gap (approximately 300μm) between the photosensitive drum 7 and the developing roller 9 c. Thetop surface of the recessed portion 2 i of the cleaning chamber frame 13is slanted so that the compression type coil spring 22 a is graduallycompressed when the image developing unit D and the cleaning unit C areunited. That is, the image developing unit D and the cleaning unit C arepivotable toward each other about the joining member 22, wherein thepositional relationship (gap) between the peripheral surface of thephotosensitive drum 7 and the peripheral surface of the developingroller 9 c is precisely maintained by the elastic force of thecompression type coil spring 22 a.

Since the compression type coil spring 22 a is attached to the baseportion of the arm portion 19 of the image developing chamber frame 12,the elastic force of the compression type coil spring 22 a affects onlythe base portion of the arm portion 19. In a case in which the imagedeveloping chamber frame 12 is provided with a dedicated spring mountfor the compression type coil spring 22 a, the adjacencies of the springseat must be reinforced to precisely maintain the predetermined gapbetween the photosensitive drum 7 and the developing roller 9 c.However, with the placement of the compression type coil spring 22 a inthe above described manner, it is unnecessary to reinforce theadjacencies of the spring seat, that is, the adjacencies of the baseportion of the arm portion 19. In the case of this embodiment, becausethe base portion of the arm portion 19 is inherently greater in strengthand rigidity.

The above described structure which holds together the cleaning chamberframe 13 and the image developing chamber frame 12 will be describedlater in more detail.

(Structure of Process Cartridge B Guiding Means)

Next, the means for guiding the process cartridge B when the processcartridge B is installed into, or removed from, the main assembly 14 ofan image forming apparatus will be described. This guiding means isillustrated in FIGS. 9 and 10. FIG. 9 is a perspective view of theleft-hand side of the guiding means, as seen (in the direction of anarrow mark X) from the side from which the process cartridge B isinstalled into the main assembly 14 of the image forming apparatus A (asseen from the side of the image developing unit D side). FIG. 10 is aperspective view of the right-hand side of the same, as seen from thesame side.

Referring to FIGS. 4, 5, 6 and 7, each lengthwise end of the cleaningframe portion 13 is provided with means which serves as a guide when theprocess cartridge B is installed into, or removed from, the apparatusmain assembly 14. This guiding means is constituted of a cylindricalguides 13 aR and 13 aL as a cartridge positioning guiding member, androtation controlling guides 13 bR and 13 bL as means for controlling theattitude of the process cartridge B when the process cartridge B isinstalled or removed.

As illustrated in FIG. 5, the cylindrical guide 13 aR is a hollowcylindrical member. The rotation controlling guides 13 bR is integrallyformed together with the cylindrical guide 13 aR, and radially protrudesfrom the peripheral surface of the cylindrical guide 13 aR. Thecylindrical guide 13 aR is provided with a mounting flange 13 aR1 whichis also integral with the cylindrical guide 13 aR. Thus, the cylindricalguide 13 aR, the rotation controlling guide 13 bR, and the mountingflange 13 aR1 constitute the right-hand side guiding member 13R, whichis fixed to the cleaning chamber frame 13 with small screws 13 aR2 putthrough the screw holes of the mounting flange 13 aR1. With theright-hand side guiding member 13R being fixed to the cleaning chamberframe 13, the rotation controlling guide 13 bR extends over the lateralwall of the developing means gear holder 40 fixed to the imagedeveloping chamber frame 12.

Referring to FIG. 11, a drum shaft member is constituted of a drum shaftportion 7 a inclusive of a larger diameter portion 7 a 2, a disk-shapedflange portion 29 and a cylindrical guide portion 13 aL. The largerdiameter portion 7 a 2 is fitted in the hole 13 k 1 of the cleaningframe portion 13. The flange portion 29 is engaged with a positioningpin 13 c projecting from the side wall of the lengthwise end wall of thecleaning frame portion 13, being prevented from rotating, and is fixedto the cleaning frame portion 13 with the use of small screws 13 d. Thecylindrical guide 13 aL projects outward (toward front, that is, thedirection perpendicular to the page of FIG. 6). The aforementionedstationary drum shaft 7 a which rotatively supports a spur gear 7 nfitted around the photosensitive drum 7 projects inwardly from theflange 29 (FIG. 11). The cylindrical guide 13 aL and the drum shaft 7 aare coaxial. The flange 29, the cylindrical guide 13 aL, and the drumshaft 7 a, are integrally formed of metallic material such as steel.

Referring to FIG. 6, there is a rotation controlling guide 13 bLslightly away from the cylindrical guide 13 aL. It is long and narrow,extending substantially in the radial direction of the cylindrical guide13 aL and also projecting outward from the cleaning chamber frame 13. Itis integrally formed with the cleaning chamber frame 13. In order toaccommodate this rotation controlling guide 13 bL, the flange 29 isprovided with a cutaway portion. The distance the rotation controllingguide 13 bL projects outward is such that its end surface issubstantially even with the end surface of the cylindrical guide 13 aL.The rotation controlling guide 13 bL extends over the side wall of thedeveloping roller bearing box 9 v fixed to the image developing chamberframe 12. As is evident from the above description, the left-hand sideguiding member 13L is constituted of two separate pieces: the metalliccylindrical guide 13 aL and the rotation controlling guide 13 bL ofsynthetic resin.

Next, a regulatory contact portion 13 j, which is a part of the topsurface of the cleaning chamber frame 13, will be described. In thefollowing description of the regulatory contact portion 13 j, “topsurface” means the surface which faces upward when the process cartridgeB is in the main assembly 14 of an image forming apparatus.

Referring to FIGS. 4-7, two portions 13 j of the top surface 13 i of thecleaning unit C, which are the portions right next to the right and leftfront corners 13 p and 13 q, relative to the direction perpendicular tothe direction in which the process cartridge B is inserted, constitutethe regulatory contact portions 13 j, which regulate the position andattitude of the process cartridge B when the cartridge B is installedinto the main assembly 14. In other words, when the process cartridge Bis installed into the main assembly 14, the regulatory contact portion13 j comes in contact with the fixed contact member 25 provided in themain assembly 14 of an image forming apparatus (FIGS. 9, 10 and 30), andregulates the rotation of the process cartridge B about the cylindricalguide 13 aR and 13 aL.

Next, the guiding means on the main assembly side 14 will be described.Referring to FIG. 1, as the lid 35 of the main assembly 14 of an imageforming apparatus is pivotally opened about a supporting point 35 a inthe counterclockwise direction, the top portion of the main assembly 14is exposed, and the process cartridge accommodating portion appears asillustrated in FIGS. 9 and 10. The left and right internal walls of theimage forming apparatus main assembly 14, relative to the direction inwhich the process cartridge B is inserted, are provided with guidemembers 16L (FIG. 9) and 16R (FIG. 10), respectively, which extenddiagonally downward from the side opposite to the supporting point 35 a.

As shown in the drawings, the guide members 16L and 16R comprise guideportions 16 a and 16 c, and positioning grooves 16 b and 16 d connectedto the guide portions 16 a and 16 c, respectively. The guide portions 16a and 16 c extend diagonally downward, as seen from the directionindicated by an arrow mark X, that is, the direction in which theprocess cartridge B is inserted. The positioning grooves 16 b and 16 dhave a semicircular cross-section which perfectly matches thecross-section of the cylindrical guides 13 aL or 13 aR of the processcartridge B. After the process cartridge B is completely installed inthe apparatus main assembly 14, the centers of semicircularcross-sections of the positioning groove 16 b and 16 d coincide with theaxial lines of the cylindrical guides 13 aL and 13 aR, respectively, ofthe process cartridge B, and hence, with the axial line of thephotosensitive drum 7.

The width of the guide portions 16 a and 16 c as seen from the directionin which the process cartridge B is installed or removed is wide enoughto allow the cylindrical guides 13 aL and 13 aR to ride on them with areasonable amount of play. Therefore, the rotation controlling guide 13bL and 13 bR which are narrower than the diameter of the cylindricalguide 13 aL and 13 aR naturally fit more loosely in the guide portions16 a and 16 c than the cylindrical guides 13 aL and 13 aR, respectively,yet their rotation is controlled by the guide portions 16 a and 16 c. Inother words, when the process cartridge B is installed, the angle of theprocess cartridge B is kept within a predetermined range. After theprocess cartridge B is installed in the image forming apparatus mainassembly 14, the cylindrical guides 13 aL and 13 aR of the processcartridge B are in engagement with the positioning grooves 16 b and 16 dof the guiding members 16L and 16R, and the left and right regulatorycontact portions 13 j located at the front portion, relative to thecartridge inserting direction, of the cleaning chamber frame 13 of theprocess cartridge B, are in contact with the fixed positioning members25, respectively.

The weight distribution of the process cartridge B is such that when theline which coincides with the axial lines of the cylindrical guide 13 aLand 13 aR is level, the image developing unit D side of the processcartridge B generates a larger moment about this line than the cleaningunit C side.

The process cartridge B is installed into the image forming apparatusmain assembly 14 in the following manner. First, the cylindrical guides13 aL and 13 aR of the Process cartridge B are inserted into the guideportion 16 a and 16 c, respectively, of the cartridge accommodatingportion in the image forming apparatus main assembly 14 by grasping therecessed portion 17 and ribbed portion 11 c of the process cartridge Bwith one hand, and the rotation controlling guides 13 bL and 13 bR arealso inserted into the guide portions 16 a and 16 c, tilting-downwardthe front portion, relative to the inserting direction, of the processcartridge B. Then, the process cartridge B is inserted farther with thecylindrical guides 13 aL and 13 aR and the rotation controlling guides13 bL and 13 bR of the process cartridge B following the guide portions16 a and 16 c, respectively, until the cylindrical guides 13 aL and 13aR reach the positioning grooves 16 b and 16 d of the image formingapparatus main assembly 14. Then, the cylindrical guides 13 aL and 13 aRbecome seated in the positioning grooves 16 b and 16 d, respectively,due to the weight of the process cartridge B itself; the cylindricalguides 13 aL and 13 aR of the process cartridge B are accuratelypositioned relative to the positioning grooves 16 b and 16 d. In thiscondition, the line which coincides with the axial lines of thecylindrical guides 13 aL and 13 aR also coincides with the axial line ofthe photosensitive drum 7, and therefore, the photosensitive drum 7 isreasonably accurately positioned relative to the image forming apparatusmain assembly 14. It should be noted here that the final positioning ofthe photosensitive drum 7 relative to the image forming apparatus mainassembly 14 occurs at the same time as the coupling between the two iscompleted.

Also in this condition, there is a slight gap between the stationarypositioning member 25 of the image forming apparatus main assembly 14and the regulatory contact portion 13 j of the process cartridge B. Atthis point of time, the process cartridge B is released from the hand.Then, the process cartridge B rotates about the cylindrical guides 13 aLand 13 aR in the direction to lower the image developing unit D side andraise the cleaning unit C side until the regulatory contact portions 13j of the process cartridge B come in contact with the correspondingstationary positioning members 25. As a result, the process cartridge Bis accurately positioned relative to the image forming apparatus mainassembly 14. Thereafter, the lid 35 is closed by rotating it clockwiseabout the supporting point 35 a.

In order to remove the process cartridge B from the apparatus mainassembly 14, the above described steps are carried out in reverse. Morespecifically, first, the lid 35 of the apparatus main assembly 14 isopened, and the process cartridge B is pulled upward by grasping theaforementioned top and bottom ribbed portions 11 c, that is, thehandhold portions, of the process cartridge by hand. Then, thecylindrical guides 13 aL and 13 aR of the process cartridge B rotate inthe positioning grooves 16 b and 16 d of the apparatus main assembly 14.As a result, the regulatory contact portions 13 j of the processcartridge B separate from the corresponding stationary positioningmember 25. Next, the process cartridge B is pulled more. Then, thecylindrical guides 13 aL and 13 aR come out of the positioning grooves16 b and 16 d, and move into the guide portions 16 a and 16 c of theguiding member 16L and 16R, respectively, fixed to the apparatus mainassembly 14. In this condition, the process cartridge B is pulled more.Then, the cylindrical guides 13 aL and 13 aR and the rotationcontrolling guides 13 bL and 13 bR of the process cartridge B slidediagonally upward through the guide portions 16 a and 16 c of theapparatus main assembly 14, with the angle of the process cartridge Bbeing controlled so that the process cartridge B can be completely movedout of the apparatus main assembly 14 without making contact with theportions other than the guide portions 16 a and 16 c.

Referring to FIG. 12, the spur gear 7 n is fitted around one of thelengthwise ends of the photosensitive drum 7, which is the end oppositeto where the helical drum gear 7 b is fitted. As the process cartridge Bis inserted into the apparatus main assembly 14, the spur gear 7 nmeshes with a gear (shown in phantom) coaxial with the imagetransferring roller 4 located in the apparatus main assembly, andtransmits from the process cartridge B to the transferring roller 4 thedriving force which rotates the transferring roller 4.

(Toner Chamber Frame)

Referring to FIGS. 3, 5, 7, 16, 20 and 21, the toner chamber frame willbe described in detail. FIG. 20 is a perspective view of the tonerchamber frame as seen before a toner seal is welded on, and FIG. 21 is aperspective view of the toner chamber frame after toner is fitted in.

Referring to FIG. 3, the toner chamber frame 11 is constituted of twoportions: the top and bottom portions 11 a and 11 b. Referring to FIG.1, the top portion 11 a bulges upward, occupying the space on the sideof the optical system 1 in the image forming apparatus main assembly 14,so that the toner capacity of the process cartridge B can be increasedwithout increasing the size of the image forming apparatus A. Referringto FIGS. 3, 4 and 7, the top portion 11 a of the toner chamber frame 11has a recessed portion 17, which is located at the lengthwise centerportion of the top portion 11 a, and serves as a handhold. An operatorof the image forming apparatus can handle the process cartridge B bygrasping it by the recessed portion 17 of the top portion 11 a and thedownward facing side of the bottom portion 11 b. The ribs 11 c extendingon the downward facing surface of the bottom portion 11 b in thelengthwise direction of the bottom portion 11 b serve to prevent theprocess cartridge B from slipping out of the operator's hand. Referringagain to FIG. 3, the flange 11 a 1 of the top portion 11 a is alignedwith the raised-edge flange 11 b 1 of the bottom portion 11 b, theflange 11 a 1 being fitted within the raised edge of the flange 11 b 1of the bottom portion 11 b, so that the walls of the top and bottomportions of the toner chamber frame 11 perfectly meet at the weldingsurface U, and then, the top and bottom portions 11 a and 11 b of thetoner chamber frame 11 are welded together by melting the welding ribswith the application of ultrasonic waves. The method for uniting the topand bottom portions 11 a and 11 b of the toner chamber frame 11 does notneed to be limited to ultrasonic welding. They may be welded by heat orforced vibration, or may be glued together. Further, the bottom portion11 b of the toner chamber frame 11 is provided with a stepped portion 11m, in addition to the flange 11 b 1 which keeps the top and bottomportions 11 a and 11 b aligned when they are welded together byultrasonic welding. The stepped portion 11 m is located above an opening11 i and is substantially in the same plane as the flange 11 b 1. Thestructures of stepped portion 11 m and its adjacencies will be describedlater.

Before the top and bottom portions 11 a and 11 b of the toner chamberframe 11 are united, a toner feeding member 9 b is assembled into thebottom portion 11 b, and a coupling member 11 e is attached the end ofthe toner feeding member 9 b through the hole 11 e 1 of the side wall ofthe toner chamber frame 11 as shown in FIG. 16. The hole 11 e 1 islocated at one of the lengthwise ends of the bottom portion 11 b, andthe side plate which has the hole 11 e 1 is also provided with a tonerfilling opening 11 d substantially shaped like a right triangle. Thetriangular rim of the toner filling opening 11 d is constituted of afirst edge, which is one of two edges that are substantiallyperpendicular to each other, and extends along the joint between the topand bottom portion 11 a and 11 b of the toner chamber frame 11, a secondedge which vertically extends in the direction substantiallyperpendicular to the first edge, and a third edge, that is, a diagonaledge, which extends along the slanted edge of the bottom portion 11 b.In other words, the toner filling opening 11 d is rendered as large aspossible, while being located next to the hole 11 e 1. Next, referringto FIG. 20, the toner chamber frame 11 is provided with an opening 11 ithrough which toner is fed from the toner chamber frame 11 into theimage developing chamber frame 12, and a seal (which will be describedlater) is welded to seal this opening 11 i. Thereafter, toner is filledinto the toner chamber frame 11 through the toner filling opening 11 d,and then, the toner filling opening 11 d is sealed with a toner sealingcap 11 f to finish a toner unit J. The toner sealing cap 11 f is formedof polyethylene, polypropylene, or the like, and is pressed into, orglued to, the toner filling opening 11 d of the toner chamber frame 11so that it does not come off. Next, the toner unit J is welded to theimage developing chamber frame 12, which will be described later, byultrasonic welding, to form the image developing unit D. The means foruniting the toner unit J and the image developing unit D is not limitedto ultrasonic welding; it may be gluing or snap-fitting which utilizesthe elasticity of the materials of the two units.

Referring to FIG. 3, the slanted surface K of the bottom portion 11 b ofthe toner chamber frame 11 is given an angle of θ so that the toner inthe top portion of the toner chamber frame 11 naturally slides down asthe toner at the bottom is consumed. More specifically, it is desirablethat the angle θ formed between the slanted surface K when the processcartridge B is in the apparatus main assembly 14 and the horizontal lineZ is approximately 65 deg. when the apparatus main assembly 14 ishorizontally placed. The bottom portion 11 b is given an outwardlybulging portion 11 g so that it does not interfere with the rotation ofthe toner feeding member 9 b. The diameter of the sweeping range of thetoner feeding member 9 b is approximately 37 mm. The height of thebulging portion 11 g has only to be approximately 0-10 mm from theimaginary extension of the slanted surface K. This is due to thefollowing reason: if the bottom surface of the bulging portion 11 g isabove the imaginary extension of the slanted surface K, the toner which,otherwise, naturally slides down from the top portion of the slantedsurface K and is fed into the image developing chamber frame 12,partially fails to be fed into the image developing chamber frame 12,collecting in the area where the slanted surface K and the outwardlybulging portion 11 g meet. Contrarily, in the case of the toner chamberframe 11 in this embodiment, the toner is reliably fed into the imagedeveloping chamber frame 12 from the toner chamber frame 11.

The toner feeding member 9 b is formed of a steel rod having a diameterof approximately 2 mm, and is in the form of a crank shaft. Referring toFIG. 20 which illustrates one end of the toner feeding member 9 b, one 9b 1 of the journals of the toner feeding member 9 b is fitted in a hole11 r which is located in the toner chamber frame 11, adjacent to theopening 11 i of the toner chamber frame 11. The other of the journals isfixed to the coupling member 11 e (where the journal is fixed to thecoupling member 11 e is not visible in FIG. 20).

As described above, providing the bottom wall of the toner chamber framesection 11 with the outwardly bulging portion 11 g as the sweeping spacefor the toner feeding member 9 b makes it possible to provide theprocess cartridge B with stable toner feeding performance without costincrease.

Referring to FIGS. 3, 20 and 22, the opening 11 i through which toner isfed from the toner chamber frame section 11 into the development chamberframe section is located at the joint between the toner chamber framesection 11 and the development chamber frame section 12. The opening 11i is surrounded by an recessed surface 11 k which in turn is surroundedby the top and bottom portions 11 j and 11 j 1 of the flange of thetoner chamber frame 11. The lengthwise outer (top) edge of the topportion 11 j and the lengthwise outer (bottom) edge of the bottomportion 11 j 1 are provided with grooves 11 n, respectively, which areparallel to each other. The top portion 11 j of the flange above therecessed surface 11 k is in the form of a gate, and the surface of thebottom portion 11 j 1 of the flange is perpendicular to the surface ofthe recessed surface 11 k. Referring to FIG. 22, the plane of the bottomsurface 11 n 2 of the groove 11 n is on the outward side (toward theimage developing chamber frame 12) of the surface of the recessedsurface 11 k. However, the flange of the toner chamber frame 11 may bestructured like the flange illustrated in FIG. 39 in which the top andbottom portion 11 j of the flanges are in the same plane and surroundthe opening 11 i like the top and bottom pieces of a picture frame.

Referring to FIG. 19, an alphanumeric reference 12 u designates one ofthe flat surfaces of the image developing chamber frame 12, which facesthe toner chamber frame 11. The flange 12 e which is parallel to theflat surface 12 u and surrounds all four edges of this flat surface 12 ulike a picture frame is provided at a level slightly recessed from theflat surface 12 u. The lengthwise edges of the flange 12 e are providedwith a tongue 12 v which fit into the groove 11 n of the toner chamberframe 11. The top surface of the tongue 12 v is provided with an angularridge 12 v 1 (FIG. 22) for ultrasonic welding. After the variouscomponents are assembled into the toner chamber frame 11 and imagedeveloping chamber frame 12, the tongue of the image developing chamberframe 12 is fitted into the groove 11 n of the toner chamber frame 11,and the two frames 11 and 12 are welded together along the tongue 12 vand groove 11 n (detail will be given later).

Referring to FIG. 21, a cover film 51, which can be easily torn in thelengthwise direction of the process cartridge B, is pasted to therecessed surface 11 k to seal-the opening 11 i of the toner chamberframe 11; it is pasted to the toner chamber frame 11, on the recessedsurface 11 k, alongside the four edges of the opening 11. In order tounseal the opening 11 i by tearing the cover film 51, the processcartridge B is provided with a tear tape 52, which is welded to thecover film 51. The cover tape 52 is doubled back from the lengthwise end52 b of the opening 11 i, is put between an elastic sealing member 54,such as a piece of felt (FIG. 19), and the opposing surface of the tonerchamber frame 11, at the end opposite to the end 52 b, and is slightlyextended from the process cartridge B. The slightly extended end portion52 a of the tear tape 52 is adhered to a pull-tab 11 t which is to begrasped by hand (FIGS. 6, 20 and 21). The pull-tab 11 t is integrallyformed with the toner chamber frame 11, wherein the joint portionbetween the pull-tab 11 t and the toner chamber frame 11 issubstantially thin so that the pull-tab 11 t can be easily torn awayfrom the toner chamber frame 11. The surface of the sealing member 54except for the peripheral areas, is covered with a synthetic resin filmtape 55 having a small friction coefficient. The tape 55 is pasted tothe sealing member 54. Further, the flat surface 12 e located at theother of the lengthwise end portions of the toner chamber frame 11, thatis, the end portion opposite to the position where the elastic sealingmember 54 is located, is covered with the elastic sealing member 56,which is pasted to the flat surface 12 e (FIG. 19).

The elastic sealing members 54 and 56 are pasted on the flange 12 e, atthe corresponding lengthwise ends, across the entire width of the flange12 e. As the toner chamber frame 11 and the image developing chamberframe 12 are joined, the elastic sealing members 54 and 56 exactly coverthe corresponding lengthwise end portions of the flange 11 j surroundingthe recessed surface 11 k, across the entire width the flange 11 j,overlapping with the tongue 12 v.

Further, in order to precisely position the toner chamber frame 11 andthe image developing chamber frame 12 relative to each other when theyare joined, the flange 11 j of the toner chamber frame 11 is providedwith a round hole 11 r and a square hole 11 q which engage with thecylindrical dowel 12 w 1 and square dowel 12 w 2, respectively, of theimage developing chamber frame 12. The round hole 11 r tightly fits withthe dowel 12 w 1, whereas the square hole 11 q loosely fits with thedowel 12 w 2 in terms of the lengthwise direction while tightly fittingtherewith in terms of the other direction.

The toner chamber frame 11 and the image developing chamber frame 12 areindependently assembled as a compound component prior to a process inwhich they are united. Then, they are united in the following manner.First, the cylindrical positioning dowel 12 w 1 and square positioningdowel 12 w 2 of the image developing chamber frame 12 are fitted intothe positioning round hole 11 r and positioning square hole 11 q of thetoner chamber frame 11, and the tongue 12 v of the image developingchamber frame 12 is placed in the groove 11 n of the toner chamber frame11. Then, the toner chamber frame 11 and the image developing chamberframe 12 are pressed toward each other. As a result, the sealing members54 and 56 come in contact with, and are compressed by, the correspondinglengthwise end portions of the flange 11 j. At the same time, rib-likeprojections 12 z, which are located, as a spacer, at each lengthwise endof the flat surface 12 u of the image developing chamber frame 12, arepositioned close to the flange 11 j of the toner chamber frame 11. Therib-like protections 12 z are integrally formed with the imagedeveloping chamber frame 12, and are located at both sides, relative tothe lengthwise direction, of the tear tape 52, so that the tear tape canbe passed between the opposing projections 12 z.

With the toner chamber frame 11 and the image developing chamber frame12 being pressed toward each other as described above, ultrasonicvibration is applied between the tongue-like portion 12 v and the groove11 n. As a result, the angular ridge 12 v 1 is melt by frictional heatand fuses with the bottom of the groove 11 n. Consequently, the rimportion 11 n 1 of the groove 11 n of the toner chamber frame 11 and therib-like projection 12 z of the image developing chamber frame 12 remainin airtight contact with each other, leaving a space between therecessed surface 11 k of the toner chamber frame 11 and the flat surface12 u of the image developing chamber frame 12. The aforementioned coverfilm 51 and tear tape 52 fit in this space.

In order to feed the toner stored in the toner chamber frame 11 into theimage developing chamber frame 12, the opening 11 i of the toner chamberframe 11 must be unsealed. This is accomplished in the following manner.First, the pull-tab 11 t attached to the end portion 5Za (FIG. 6) of thetear tape 52 extending from the process cartridge B is cut loose, ortorn loose, from the toner chamber frame 11, and then, is pulled by handby an operator. This will tear away the cover film 51 to unseal theopening 11 i, enabling the toner to be fed from the toner chamber frame11 into the image developing chamber frame 12. After the cover film 52is pulled out of the process cartridge B, the lengthwise ends of thecartridge B are kept sealed by the elastic seals 54 and 56 which arelocated at the corresponding lengthwise ends of the flange 11 j of thetoner chamber frame 11. Since the elastic sealing members 54 and 56 aredeformed (compressed) only in the direction of their thickness whilemaintaining their hexahedral shapes, they can keep the process cartridgesealed very effectively.

Since the side of the toner chamber frame 11, which faces the imagedeveloping chamber frame 12, and the side of the image developingchamber frame 12, which faces the toner chamber frame 11, are structuredas described above, the tear tape 52 can be smoothly pulled out frombetween the two frames 11 and 12 by simply applying to the tear tape 52a force strong enough to tear the cover film 51.

As described above, when the toner chamber frame 11 and the imagedeveloping chamber frame 12 are united, a welding method employingultrasound is employed to generate frictional heat which melts theangular ridge 12 v 1. This frictional heat is liable to cause thermalstress in the toner chamber frame 11 and the image developing chamberframe 12, and these frames may become deformed due to the stress.However, according to this embodiment, the groove 1 in of the tonerchamber frame 11 and the tongue 12 v of the image developing chamberframe 12 engage with each other across the almost entire length oftheirs. In other words, as the two frames 11 and 12 are united, thewelded portion and its adjacencies are reinforced, and therefore, thetwo frames are not likely to be deformed by the thermal stress.

As for the material for the toner chamber frame 11 and the imagedeveloping chamber frame 12, plastic material is used; for example,polystyrene, ABS resin (acrylonitrile-butadiene-styrene), polycarbonate,polyethylene, polypropylene, and the like.

Referring to FIG. 3, this drawing is a substantially verticalcross-section of the toner chamber frame 11 of the process cartridge Bin this embodiment, and illustrates the interface between the tonerchamber frame 11 and the image developing chamber frame 12, and itsadjacencies.

At this time, the toner chamber frame 11 of the process cartridge B inthis embodiment will be described in more detail with reference to FIG.3. The toner held in a toner container 11A is single component toner. Inorder to allow this toner to efficiently free fall toward the opening 11i, the toner chamber frame 11 is provided with slanted surfaces K and L,which extend across the entire length of the toner chamber frame 11. Theslanted surface L is above the opening 11 i, and the slanted surface Kis in the rear of the toner chamber frame 11 as seen from the opening 11i (in the widthwise direction of the toner chamber frame 11). Theslanted surfaces L and K are parts of the top and bottom pieces 11 a and11 b, respectively, of the toner chamber frame 11. After the processcartridge B is installed in the apparatus main assembly 14, the slantedsurface L faces diagonally downward, and the slanted surface K facesdiagonally upward, an angle Θ3 between the slanted surface K and theline m perpendicular to the interface between the toner chamber frame 11and the image developing chamber frame 12 being approximately 20 deg.-40deg. In other words, in this embodiment, the configuration of the topportion 11 a of the toner chamber frame 11 is designed so that theslanted surfaces K and L hold the aforementioned angles, respectively,after the top and bottom portions 11 a and 11 b of the toner chamberframe 11 are united. This, according to this embodiment, the tonercontainer 11A holding the toner is-enabled to efficiently feed the tonertoward the opening 11 i.

Next, the image developing chamber frame will be described in detail.

(Image Developing Chamber Frame)

The image developing chamber frame 12 of the process cartridge B will bedescribed with reference to FIGS. 3, 14, 15, 16, 17, and 18. FIG. 14 isa perspective view depicting the way various components are assembledinto the image developing chamber frame 12; FIG. 15, a perspective viewdepicting the way a developing station driving force transmitting unitDG is assembled into the image developing chamber frame 12; FIG. 16, aside view of the development unit before the driving force transmittingunit DG is attached; FIG. 17, a side view of the developing stationdriving force transmitting unit DG as seen from inside the imagedeveloping chamber frame 12; and FIG. 18 is a perspective view of thebearing box as seen from inside.

As described before, the developing roller 9 c, the developing blade 9d, the toner stirring member 9 e, and the rod antenna 9 h for detectingthe toner remainder, are assembled into the image developing chamberframe 12.

Referring to FIG. 14, the developing blade 9 d comprises anapproximately 1-2 mm thick metallic plate 9 d 1, and an urethane rubber9 d 2 glued to the metallic plate 9 d 1 with the use of hot melt glue,double-side adhesive tape, or the like. It regulates the amount of thetoner to be carried on the peripheral surface of the developing roller 9c as the urethane rubber 9 d 2 is placed in contact with the generatrixof the developing roller 9 c. The lengthwise ends of the blade mountingreference flat surface 12 i, as a blade mount, of the image developingchamber frame 12, are provided with a dowel 12 i 1, a square projection12 i 3, and a screw hole 12 i 2. The dowel 12 i 1 and the projection 12i 3 are fitted in a hole 9 d 3 and a notch 9 d 5, respectively, of themetallic plate 9 d 1. Then, a small screw 9 d 6 is put through a screwhole 9 d 4 of the metallic plate 9 d 1, and is screwed into theaforementioned screw hole 12 i 2 with female threads, to fix themetallic plate 9 d 1 to the flat surface 12 i. In order to prevent tonerfrom leaking out, an elastic sealing member 12 s formed of MOLTPLANE, orthe like, is pasted to the image developing chamber frame 12, along thelengthwise top edge of the metallic plate 9 d 1. Also, an elasticsealing member 12 s 1 is pasted to the developing chamber frame 12,along the edge 12 j of the curved bottom wall portion which accommodatesthe developing roller 9 c, starting from each lengthwise end of theelastic sealing member 12 s. Further, a thin elastic sealing member 12 s2 is pasted to the image developing chamber frame 12, along amandible-like portion 12 h, in contact with the generatrix of thedeveloping roller 9 c.

The metallic plate 9 d 1 of the developing blade 9 d is bent 90 deg. onthe side opposite to the urethane rubber 9 d 2, forming a bent portion 9d 1 a.

Next, referring to FIGS. 14 and 18, the image developing roller unit Gwill be described. The image developing roller unit G comprises: (1)image developing roller 9 c; (2) spacer roller 9 i for keeping constantthe distance between the peripheral surfaces of the developing roller 9c and the photosensitive drum 7, being formed of electrically insulativesynthetic resin and doubling as a sleeve cap which covers the developingroller 9 c at each lengthwise end to prevent electrical leak between thealuminum cylinder portions of the photosensitive drum 7 and thedeveloping roller 9 c; (3) developing roller bearing 9 j (illustrated inenlargement in FIG. 14); (4) developing roller gear 9 k (helical gear)which receives driving force from a helical drum gear 7 b attached tothe photosensitive drum 7 and rotates the developing roller 9 c; (5) acoil spring type contact 9 l, one end of which is in contact with oneend of the developing roller 9 c (FIG. 18); and (6) a magnet 9 g whichis contained in the developing roller 9 c to adhere the toner onto theperipheral surface of the developing roller 9 c. In FIG. 14, the bearingbox 9 v has been already attached to the developing roller unit G.However, in some cases, the developing roller unit G is first disposedbetween the side plates 12A and 12B of the image developing chamberframe 12, and then is united with the bearing box 9 v when the bearingbox 9 v is attached to the image developing chamber frame 12.

Referring again to FIG. 14, in the developing roller unit G, thedeveloping roller 9 c is rigidly fitted with a metallic flange 9 p atone lengthwise end. This flange 9 p has a developing roller gear shaftportion 9 p 1 which extends outward in the lengthwise direction of thedeveloping roller 9 c. The developing roller gear shaft portion 9 p 1has a flattened portion, with which the developing roller gear 9 kmounted on the developing gear shaft portion 9 p 1 is engaged, beingprevented from rotating on the developing roller gear shaft portion 9 p1. The developing roller gear 9 k is a helical gear, and its teeth areangled so that the thrust generated by the rotation of the helical gearis directed toward the center of the developing roller 9 c (FIG. 38).One end of the shaft of the magnet 9 g, which is shaped to give it aD-shaped cross-section, projects outward through the flange 9 p, andengages with the developing means gear holder 40 to be nonrotativelysupported. The aforementioned developing roller bearing 9 j is Providedwith a round hole having a rotation preventing projection 9 j 5 whichprojects into the hole, and in this round hole, the C-shaped bearing 9 j4 perfectly fits. The flange 9 p rotatively fits in the bearing 9 j 4.The developing roller bearing 9 j is fitted into a slit 12 f of theimage developing chamber frame 12, and is supported there as thedeveloping means gear holder 40 is fixed to the image developing chamberframe 12 by putting the projections 40 g of the developing means gearholder 40 through the corresponding-holes 9 j 1 of the developing rollergear bearing 9 j, and then inserting them in the corresponding holes 12g of the image developing chamber frame 12. The bearing 9 j 4 in thisembodiment has a C-shaped flange. However, there will be no problem evenif the cross-section of the actual bearing portion of the bearing 9 j 4is C-shaped. The aforementioned hole of the development roller bearing 9j, in which the bearing 9 p 1 fits, has a step. In other words, it isconsisted of a large diameter portion and a small diameter portion, andthe rotation preventing projection 9 j 5 is projecting from the wall ofthe large diameter portion in which the flange of the bearing 9 j 4 fit.The material for the bearing 9 j, and the bearing 9 f which will bedescribed later, is polyacetal, polyamide, or the like.

Although substantially encased in the developing roller 9 c, the magnet9 g extends from the developing roller 9 c at both lengthwise ends, andis fitted in a D-shaped supporting hole 9 v 3 of the developing rollerbearing box 9 v illustrated in FIG. 18, at the end 9 g 1 having theD-shaped cross-section. In FIG. 18, the D-shaped supporting hole 9 v 3,which is located in the top portion of the developing roller bearing box9 v, is not visible. At one end of the developing roller 9 c, a hollowjournal 9 w formed of electrically insulative material is immovablyfitted within the developing roller 9 c, in contact with the internalperipheral surface. A cylindrical portion 9 w 1 which is integral withthe journal 9 w and has a smaller diameter than the journal 9 welectrically insulates the magnet 9 g from a coil spring type contact 9l which is electrically in contact with the developing roller 9 c. Thebearing 9 f with the aforementioned flange is formed of electricallyinsulative synthetic resin, and fits in the bearing accommodating hole 9v 4 which is coaxial with the aforementioned magnet supporting hole 9 v3. A key portion 9 f 1 integrally formed with the bearing 9 f fits in akey groove 9 v 5 of the bearing accommodating hole 9 v 4, preventing thebearing 9 f from rotating.

The bearing accommodating hole 9 v 4 has a bottom, and on this bottom, adoughnut-shaped development bias contact 121 is disposed. As thedeveloping roller 9 c is assembled into the developing roller bearingbox 9 v, the metallic coil spring type contact 9 l comes in contact withthis doughnut-shaped development bias contact 121, and is compressed,establishing thereby electrical connection. The doughnut-shapeddevelopment bias contact 121 has a lead which comprises: a first portion121 a which perpendicularly extends from the outer periphery of thedoughnut-shaped portion, fitting in the recessed portion 9 v 6 of thebearing accommodating hole 9 v 4, and runs along the exterior wall ofthe bearing 9 f up to the cutaway portion 9 v 7 located at the edge ofthe bearing accommodating hole 9 v 4; a second portion 121 b which runsfrom the cutaway portion, being bent outward at the cutaway portion; athird portion 121 c which is bent from the second portion 121 b; afourth portion 121 d which is bent from the third portion 121 c in theoutward, or radial, direction of the developing roller 9 c; and anexternal contact portion 121 e which is bent from the fourth portion 121d in the same direction. In order to support the development biascontact 121 having the above described shape, the developing rollerbearing box 9 v is provided with a supporting portion 9 v 8, whichprojects inward in the lengthwise direction of the developing roller 9c. The supporting portion 9 v 8 is in contact with the third and fourthportion 121 c and 121 d, and the external contact portion 121 e, of thelead of the development bias contact 121. The second portion 121 b isprovided with an anchoring hole 121 f, into which a dowel 9 v 9projecting inward from the inward facing wall of the developing rollerbearing box 9 v in the lengthwise direction of the developing roller 9 cis pressed. The external contact portion 121 e of the development biascontact 121 comes in contact with the development bias contact member125 of the apparatus main assembly 14 as the process cartridge B isinstalled in the apparatus main assembly 14, so that development bias isapplied to the developing roller 9 c. The development bias contactmember 125 will be described later.

Two cylindrical projections 9 v 1 of the developing roller bearing box 9v are fitted into the corresponding holes 12 m of the image developingchamber frame 12, which are provided at the lengthwise end asillustrated in FIG. 19. As a result, the developing roller gearing box 9v is precisely positioned on the image developing chamber frame 12.Then, an unillustrated small screw is put through each screw hole of thedeveloping roller bearing box 9 v, and then is screwed into thefemale-threaded screw hole 12 c of the image developing chamber frame 12to fix the developing roller bearing box 9 v to the image developingchamber frame 12.

As is evident from the above description, in this embodiment, in orderto mount the developing roller 9 c in the image developing chamber frame12, the developing roller unit G is assembled first, and then, theassembled developing roller unit G is attached to the image developingchamber frame 12.

The developing roller unit G is assembled following the steps describedbelow. First, the magnet 9 g is put through the developing roller 9 cfitted with the flange 9 p, and the journal 9 w and the coil spring typecontact 9 l for development bias are attached to the end of thedeveloping roller 9 c. Thereafter, the spacer roller 9 i and thedeveloping roller bearing 9 j are fitted around each lengthwise endportion of the developing roller 9 c, the developing roller bearing 9 jbeing on the outer side relative to the lengthwise direction of thedeveloping roller 9 c. Then, the developing roller gear 9 k is mountedon the developing roller gear shaft portion 9 p 1 located at the end ofthe developing roller 9 c. It should be noted here that the lengthwiseend 9 g 1 of the magnet 9 g, which has a D-shaped cross-section,projects from the developing roller 9 c, on the side where thedeveloping roller gear 9 k is attached; it projects from the end of thecylindrical portion 9 w 1 of the hollow journal 9 w.

Next, the rod antenna 9 h for detecting the toner remainder will bedescribed. Referring to FIGS. 14 and 19, one end of the rod antenna 19 his bent like that of a crank shaft, wherein the portion comparable tothe arm portion of the crank shaft constitutes a contact portion 9 h 1(toner remainder detecting contact 122), and must be electrically incontact with the toner detecting contact member 126 attached to theapparatus main assembly 14. The toner detection contact member 126 willbe described later. In order to mount the rod antenna 9 h in the imagedeveloping chamber frame 12, the rod antenna 9 h is first inserted intothe image developing chamber frame 12 through a through hole 12 b of aside plate 12B of the image developing chamber frame 12, and the endwhich is put through the hole 12 b first is placed in an unillustratedhole of the opposite side plate of the image developing chamber frame12, so that the rod antenna 9 h is supported by each side plate. Inother words, the rod antenna 9 h is properly positioned by the throughhole 12 b and the unillustrated hole on the opposite side. In order toprevent toner from invading the through hole 12 b, an unillustratedsealing member (for example, a ring formed of synthetic resin, a pieceof felt or sponge, or the like) is insert in the through hole 12 b.

As the developing roller gear box 9 v is attached to the imagedeveloping chamber frame 12, the contact portion 9 h 1 of the rodantenna 9 h, that is, the portion comparable to the arm portion of acrank shaft, is positioned so that the rod antenna 9 h is prevented frommoving or coming out of the image developing chamber frame 12

After the toner chamber frame 11 and the image developing chamber frame12 are united, the side plate 12A of the image developing chamber frame12, through which the rod antenna 9 h is inserted, overlaps with theside plate of the toner chamber frame 11, partially covering the tonersealing cap 11 f of the bottom portion 11 b of the toner chamber frame11. Referring to FIG. 16, the side plate 12A is provided with a hole 12x, and a shaft fitting portion 9 s 1 (FIG. 15) of the toner feeding gear9 s for transmitting driving force to the toner feeding member 9 b isput through this hole 12 x. The shaft fitting portion 9 s 1 is a part ofthe toner feeding gear 9 s, and is coupled with the coupling member 11 e(FIGS. 16 and 20) to transmits driving force to the toner feeding member9 b. As described before, the coupling member 11 e is engaged with oneof the lengthwise ends of the toner feeding member 9 b and is rotativelysupported by the toner chamber frame 11.

Referring to FIG. 19, in the image developing chamber frame 12, thetoner stirring member 9 e is rotatively supported in parallel to the rodantenna 9 h. The toner stirring member 9 e is also shaped like a crankshaft. One of the crank shaft journal equivalent portions of the tonerstirring member 9 e is fitted in a bearing hole (unillustrated) of theside plate 12B, whereas the other is fitted with the toner stirring gear9 m which has a shaft portion rotatively supported by the side plate 12Aillustrated in FIG. 16. The crank arm equivalent portion of the tonerstirring member 9 e is fitted in the notch of the shaft portion of thetoner stirring gear 9 m so that the rotation of the toner stirring gear9 m is transmitted to the toner stirring member 9 e.

Next, transmission of driving force to the image developing unit D willbe described.

Referring to FIG. 15, the shaft 9 g 1 of the magnet 9 g, which has theD-shaped cross-section, engages with a magnet supporting hole 40 a ofthe image developing means gear holder 40. As a result, the magnet 9 gis nonrotatively supported. As the image developing mean gear holder 40is attached to the image developing chamber frame 12, the developingroller gear 9 k meshes with a gear 9 q of a gear train GT, and the tonerstirring gear 9 m meshes with a small gear 9 s 2. Thus, the tonerfeeding gear 9 s and the toner stirring gear 9 m are enabled to receivethe driving force transmitted from the developing roller gear 9 k.

All the gears from the gear 9 q to the toner gear 9 s are idler gears.The gear 9 q which meshes with the developing roller gear 9 k, and asmall gear which is integral with the gear 9 q, are rotatively supportedon a dowel 40 b which is integral with the image developing means gearholder 40. A large gear 9 r which engages with the small gear 9 q 1, anda small gear 9 r 1 which is integral with the gear 9 r, are rotativelysupported on the dowel 40 c which is integral with the image developingmeans gear holder 40. The small gear 9 r 1 engages with the tonerfeeding gear 9 s. The toner feeding gear 9 s is rotatively supported ona dowel 40 d which is a part of the image developing means gear holder40. The toner feeding gear 9 s has the shaft fitting portion 9 s 1. Thetoner feeding gear 9 s engages with a small gear 9 s 2. The small gear 9s 2 is rotatively supported on a dowel 40 e which is a part of the imagedeveloping means gear holder 40. The dowels 40 b, 40 c, 40 d, and 40 ehave a diameter of approximately 5-6 mm, and support the correspondinggears of the gear train GT.

With the provision of the above described structure, the gears whichconstitute the gear train can be supported by a single component (imagedeveloping means gear holder 40). Therefore, when assembling the processcartridge B, the gear train GT can be partially preassembled onto theimage developing means gear holder 40; compound components can bepreassembled to simplify the main assembly process. In other words,first, the rod antenna 9 h, and the toner stirring member 9 e areassembled into the image developing chamber frame 12, and then, thedeveloping roller unit G and the gear box 9 v are assembled into thedeveloping station driving force transmission unit DG and the imagedeveloping chamber frame 12, respectively, completing the imagedeveloping unit D.

Referring to FIG. 19, an alphanumeric reference 12 p designates anopening of the image developing chamber frame 12, which extends in thelengthwise direction of the image developing chamber frame 12. After thetoner chamber frame 11 and the image developing chamber frame 12 areunited, the opening 12 p squarely meets with the opening 11 i of thetoner chamber frame 11, enabling the toner held in the toner chamberframe 11 to be supplied to the developing roller 9 c. The aforementionedtoner stirring member 9 e and rod antenna 9 h are disposed along one ofthe lengthwise edges of the opening 12 p, across the entire lengththereof.

The materials suitable for the image developing chamber frame 12 are thesame as the aforementioned materials suitable for the toner chamberframe 11.

(Structure of Electrical Contact)

Next, referring to FIGS. 8, 9, 11, 23, 30A and 30B, connection andpositioning of the contacts which establish electrical connectionbetween the process cartridge B and the image forming apparatus mainassembly 14 as the former is installed into the latter will bedescribed. A drum grounding mechanism for discharging the electriccharge on the drum 7 to the main assembly 14 will be describedhereinafter.

Referring to FIG. 8, the process cartridge B has a plurality ofelectrical contacts: (1) electrically conductive charge bias contact 120electrically connected to the charging roller shaft 8 a to apply chargebias to the charging roller 8 from the apparatus main assembly 14; (2)electrically conductive development bias contact 121 electricallyconnected to the developing roller 9 c to apply development bias to thedeveloping roller 9 c from the apparatus main assembly 14; (3)electrically conductive toner remainder detecting contact 122electrically connected to the rod antenna 9 h to detect the tonerremainder. These four contacts 119-122 are exposed from the side orbottom wall of the cartridge frame. More specifically, they all aredisposed so as to be exposed from the left wall or bottom wall of thecartridge frame, as seen from the direction from which the processcartridge B is installed, being separated from each other by apredetermined distance sufficient to prevent electrical leak. Thegrounding contact 119 and the charge bias contact 121 belong to thecleaning unit C, and the development bias contact 121 and the tonerremainder detection contact 122 belong to the image developing chamberframe 12. The toner remainder detection contact 122 doubles as a processcartridge detection contact through which the apparatus main assembly 14detects whether or not the process cartridge B has been installed in theapparatus main assembly 14.

The charge bias contact 120 and the development bias contact 121 areformed of approximately 0.1-0.3 mm thick electrically conductivemetallic plate (for example, stainless steel plate and phosphor bronzeplate), and are laid (extended) along the internal surface of theprocess cartridge. The charge bias contact 120 is exposed from thebottom wall of the cleaning unit C, on the side opposite to the sidefrom which the process cartridge B is driven. The development biascontact 121 and the toner remainder detection contact 122 are exposedfrom the bottom wall of the image developing unit D, also on the sideopposite to the side from which the process cartridge B is driven.

This embodiment will be described further in detail.

As described above, in this embodiment, the helical drum gear 7 b isprovided at one of the axial ends of the photosensitive drum 7 asillustrated in FIG. 11. The drum gear 7 b engages with the developingroller gear 9 k to rotate the developing roller 9 c. As it rotates, itgenerates thrust in the direction (indicated in an arrow mark d in FIG.11). This thrust pushes the photosensitive drum 7, which is disposed inthe cleaning chamber frame 13 with a slight play in the longitudinaldirection, toward the side on which the drum gear 7 b is mounted. As aresult, the outward edge 7 b 1 of the drum gear 7 b remains in contactwith the surface of the inward end of the bearing 38 fixed to thecleaning chamber frame 13. Thus, the position of the photosensitive drum7 relative to the process cartridge B in the axial direction of thephotosensitive drum 7 is regulated. The drum shaft 7 a extends into thebase drum 7 d (aluminum drum in this embodiment) coated with aphotosensitive layer 7 e, along the axial line.

The charge bias contact 120 is attached to the cleaning chamber frame13, adjacent to where the charging roller 8 is supported (FIG. 8).Referring to FIG. 23, the charge bias contact 120 is electrically incontact with the shaft 8 a of the charging roller 8 by way of a compoundspring 8 b which is in contact with the charge roller shaft 8 a. Thiscompound spring 8 b is constituted of a compression spring portion 8 b 1and an internal contact portion 8 b 2. The compression coil portion 8 b1 is placed between the spring seat 120 b and a charging roller bearing8 c. The internal contact portion 8 b 2 extends from the spring seatside end of the compression spring portion 8 b 1 and presses on thecharge roller shaft 8 a. The charging roller bearing 8 c is slidablyfitted in a guide groove 13 g, and the spring seat 120 b is located atthe closed end of the guiding groove 13 g. The guide groove 13 g extendsin the direction of an imaginary line which runs through the centers ofthe cross-sections of the charging roller 8 and photosensitive drum 7,the center line of the guiding groove 3 g substantially coinciding withthis imaginary line. Referring to FIG. 23, the charge bias contact 120enters the cleaning chamber frame 13 at the location 120 a where it isexposed, runs along the internal wall of the cleaning chamber frame 13,bends in the direction which intersects with the direction in which thecharge roller shaft 8 a of the charging roller 8 is moved, and ends atthe spring seat 120 b.

Next, the development bias contact 121 and the toner remainder detectioncontact 122 will be described. Both contacts 121 and 122 are disposed onthe bottom surface which faces downward when the process cartridge B isin the apparatus main assembly 14 of the image developing unit D, on thesame side as the side plate 13 k of the cleaning chamber frame 13. Theaforementioned third portion 121 e of the development contact 121, thatis, the portion exposed from the image developing unit D, is disposed soas to oppose the charge bias contact 120 across the spur gear 7 n. Asdescribed previously, the development bias contact 121 is electricallyin contact with the developing roller 9 c through the coil spring typecontact 9 l which is electrically in contact with the lengthwise end ofthe developing roller 9 c (FIG. 18).

FIG. 38 schematically illustrates the relationship between the thrustsgenerated by the drum gear 7 b and the developing roller gear 9 k andthe development bias contact 121. As stated before, the photosensitivedrum 7 is shifted in the direction of the arrow mark d in FIG. 38 as theprocess cartridge B is driven. As a result, the end surface of thephotosensitive drum 7 on the drum gear 7 b side remains in contact withthe end surface of the bearing 38 (FIG. 32) which is not illustrated inFIG. 38; the position of the photosensitive drum 7 in terms of thelengthwise direction thereof becomes fixed. On the other hand, thedeveloping roller gear 9 k which meshes with the drum gear 7 b isthrusted in the direction of an arrow mark e, which is opposite to thedirection of the arrow mark d. As a result, it presses the coil springtype contact 9 l which is pressing the development bias contact 121.Consequently, the pressure generated by the coil spring type contact 9 lin the direction of an arrow mark f, that is, in the direction to pressthe developing roller 9 c against developing roller bearing 9 j, isreduced. Thus, it is assured that the coil spring type contact 9 l andthe development bias contact 121 remain in contact with each other,while the friction between the end surfaces of the developing roller 9 cand developing roller bearing 9 j is reduced to allow the developingroller 9 c to rotate smoothly.

The toner remainder detection contact 122 illustrated in FIG. 8 isattached to the image developing chamber frame 12, being exposedupstream of development bias contact 121 relative to the direction inwhich the process cartridge B is inserted (direction of an arrow mark Xin FIG. 9). As is evident from FIG. 19, the toner remainder detectioncontact 122 is a part of the rod antenna 9 h which is formed ofelectrically conductive material such as metallic wire and is extendedin the lengthwise direction of the developing roller 9 c. As describedpreviously, the rod antenna 9 h stretches across the entire length ofthe developing roller 9 c, holding a predetermined distance from thedeveloping roller 9 c. It comes in contact with the toner detectioncontact member 126 of the apparatus main assembly 14 as the processcartridge B is inserted into the apparatus main assembly 14. Thecapacitance between the rod antenna 9 h and the developing roller 9 cchanges according to the amount of the toner prevent between the two.Therefore, the change in this capacitance is detected as potentialdifference by a control section (unillustrated) electrically connectedto the toner detection contact member 126 of the apparatus main assembly14 to determine the amount of the toner remainder.

The toner remainder means an amount of toner which induces apredetermined amount of capacitance when the toner is placed between thedeveloping roller 9 c and the rod antenna 9 h. In other word, thecontrol section detects that the amount of the toner in the tonercontainer 11A has been reduced to a predetermined amount; the controlsection of the apparatus main assembly 14 detects through the tonerremainder detection contact 122 that the capacitance has reached a firstpredetermined value, and therefore, determines that the amount of thetoner within the toner container 11A has dropped to a predeterminedamount. Upon detecting that the capacitance has reached the first value,the control section of the apparatus main assembly 14 informs the userthat the process cartridge B should be replaced; for example, it flashesan indicator light or sounds a buzzer. On the contrary, when the controlsection detects that the capacitance shows a predetermined second valuewhich is smaller than the predetermined first value, it determineswhether the process cartridge B has been replaced in the apparatus mainassembly 14. It does not allow the image forming operation of theapparatus main assembly 14 to be started unless it detects thecompletion of the process cartridge B installation in the apparatus mainassembly 14.

The control section may be enabled to inform the user of the absence ofthe process cartridge B in the apparatus main assembly 14, by flashingan indicator light, for example.

Next, connection between the electrical contacts of the processcartridge B and the electrical contact members of the apparatus mainassembly 14 will be described.

Referring to FIG. 9, disposed on the internal surface of on theleft-hand side wall of the cartridge accommodating space S in the imageforming apparatus A are four contact members which come in contact withthe aforementioned contacts 120-122 as the process cartridge B isinserted into the apparatus main assembles 14; a charge bias contactmember 124 which comes electrically in contact with the charge biascontact 120; a development bias contact member 125 which electricallycome in contact with the development bias contact 121; and a tonerdetection contact member 126 which comes electrically in contact withthe toner remainder detection contact 122.

As illustrated in FIG. 9, the development bias contact member 125, thetoner detection contact member 126, and the charging roller contactmember 124 are disposed, facing upward, on the bottom surface of thecartridge accommodating space S, below the guide portion 16 a andadjacent to the left-hand side wall. They are enabled to moveelastically in the vertical direction.

At this point, the positional relationship between each contact and theguide will be described.

Referring to FIG. 6 which illustrates the process cartridge B in asubstantially horizontal position, the toner remainder detection contact122 is at the lowest level. The development bias contact 121 ispositioned higher than the toner remainder detection contact 122, andthe charge bias contact 120 is positioned higher than the developmentbias contact 121. The rotation controlling guide 13 bL and thecylindrical guide 13 aL are positioned higher than the charge biascontact 120, being approximately at the same level. In terms of thedirection (indicated by the arrow mark X) in which the process cartridgeB is inserted, positioned most upstream is the toner remainder detectioncontact 122, and the rotation controlling guide 13 bL, the developmentbias contact 121, the cylindrical guide 13 aL, and the charge biascontact 120, are disposed in this order toward downstream. With theprovision of this positional arrangement, the charge bias contact 120 ispositioned close to the charging roller 8; the development bias contact121, close to the developing roller 9 c; and the toner remainderdetection contact 122, close to the rod antenna 9 h. In other words, thedistance between each contact and the related component can be reducedwithout intricately laying a long electrode in the process cartridge Band the image forming apparatus main assembly 14.

The dimension of the actual contact area of each contact is as follows.The charge bias contact 120 measures approximately 10.0 mm in both thehorizontal and vertical directions; the development bias contact 121,approximately 6.5 mm in the vertical direction and approximately 7.5 mmin the horizontal direction; and the toner remainder detection contact122, 2.0 mm in diameter and approximately 18.0 mm in the horizontaldirection. The charge bias contact 120 and the development bias contact121 are rectangular. In measuring the dimension of the contact area,“vertical” means the direction parallel to the direction X in which theprocess cartridge B is inserted, and “horizontal” means the directionperpendicular to the direction X.

The toner remainder detection contact member 126 is also an electricallyconductive plate spring. It is disposed adjacent to the guide portion 16a, being next to the guide portion 16 a in terms of the horizontaldirection, but below in terms of the vertical direction. The othercontact members 124 and 125 are also disposed adjacent to the guideportion 16 a, being slightly farther away from the guide portion 16 athan the toner remainder detection contact member 126 is terms of thehorizontal direction, and below the guide portion 16 a in terms of thevertical direction. The contact members 124 and 125 are each providedwith a compression type coil spring 129, and therefore, they projectupward from their holders 127. This arrangement will be described morespecifically referring to the charging roller contact member 124.Referring to the enlarged view of the charging roller contact member 124in FIG. 30B, the charging roller contact member 124 is placed in theholder 127 so that it is allowed to project upward from the holder 127without slipping out. Then, the holder 127 is fixed to the electricalsubstrate 128 attached to the apparatus main assembly 14. The contactmember 124 is electrically connected to the wiring pattern through anelectrically conductive compression type coil spring 129.

Before the process cartridge B inserted in the image forming apparatus Ais guided to a predetermined position by the guide portion 16 a, thecontact members 124-126 of the image forming apparatus A remainprojected by the springs as far as they are allowed to project. In thisstate, none of the contact members 124-126 is in contact with theircounterparts, that is, the contacts 120-122 of the process cartridge B.As the process cartridge B is inserted farther, the contact members124-126 come in contact with the corresponding contacts 120-122 of theprocess cartridge B one by one. Then, as the cylindrical guide 13 aL ofthe process cartridge B is fitted into the positioning groove 16 b byadditional inward movement of the process cartridge B, the contactmembers 124-126 of the apparatus main assembly 14 are pushed down by thecorresponding contacts 120-122 of the process cartridge B (in the caseof contacts 124 and 125, against the elastic force of the compressiontype coil springs 129 in the holder 127). As a result, the contactpressures between the contact members 124-126 and the correspondingcontacts 120-122 are increased.

As described above, according to this embodiment of the presentinvention, as the process cartridge B is guided to a predeterminedposition in the apparatus main assembly 14 by the guide member 16, thecontacts of the process cartridge B reliably make contact with thecontact members of the apparatus main assembly 14.

As the process cartridge B is installed in the predetermined position,the charge bias contact 120 and the charging roller contact member 124becomes electrically connected to allow high voltage (voltage composedby superposing AC voltage and DC voltage) to be applied to the chargingroller 8. The development bias contact 121 and the development biascontact member 125 make electrical connection to each other to allowhigh voltage to be applied to the developing roller 9 c. The tonerremainder detection contact 122 comes electrically in contact with thetoner detection contact member 126, and information reflecting thecapacitance between the developing roller 9 c and the rod antenna 9 h(contact 122) is transmitted to the apparatus main assembly 14 throughthe contact 122.

Further, said contacts of the process cartridge B are positioned on oneside of the cartridge frame. Therefore, the mechanical members and theelectrical wiring members of the image forming apparatus main assembly14 and the process cartridge B can be separately positioned on theappropriate sides of the cartridge accommodating space S, and theprocess cartridge B, to reduce the number of assembly steps and simplifythe maintenance.

As the lid 35 is closed after the process cartridge B is inserted intothe image forming apparatus main assembly 14, the coupling device on theprocess cartridge side connects with the coupling device on theapparatus main assembly side (discussed below) in synchronism with themovement of the lid 35, enabling the photosensitive drum 7 and the liketo receive driving force from the apparatus main assembly 14 to berotated.

Further, positioning each electrical contact in the above describedmanner makes it possible to reduce the distance the correspondingelectrode must be routed in the cartridge frame.

(Coupling and Driving Structure)

The description will be made as to a structure of coupling means whichis a drive transmission mechanism for transmitting the driving force tothe process cartridge B from the main assembly 14 of the image formingapparatus.

Referring to FIG. 11, there is shown a longitudinal sectional view of acoupling portion wherein the photosensitive drum 7 is mounted to theprocess cartridge B.

Cartridge side coupling means is provided at one longitudinal end of thephotosensitive drum 7 mounted to the process cartridge B, as shown inFIG. 11. The coupling means is in the form of a male coupling shaft 37(circular column configuration) formed on a drum flange 36 fixed to theone end of the photosensitive drum 7. The end surface 37 a 1 of theprojection 37 a is parallel with the end surface of the male shaft 37.The male shaft 37 is engageable with a bearing 38 to function as a drumshaft. In this example, the drum flange 36, male coupling shaft 37 andthe projection 37 a are integrally formed. The drum flange 36 isintegrally provided with a helical drum gear 7 b to transmit the drivingforce to the developing roller 9 c in the process cartridge B.Therefore, as shown in FIG. 11, the drum flange 36 is an integrallymolded product of plastic resin material having a drum gear (helicalgear) 7 b, male shaft 37, and the projection 37 a to constitute adriving force transmitting part having a function of transmitting adriving force.

The projection 37 a has a configuration of twisted prism, and moreparticularly, it has a cross-section of a substantially equilateraltriangle, and is gradually twisted to a small extent in the axialdirection. The corner portion of the prism is rounded. The recess 39 afor engaging with the projection 37 a has a cross-section of polygonalshape, and is gradually twisted to a small extent in the axialdirection. The projection 37 a and the recess 39 a are twisted in thesame direction with the same twisting pitch. The section of said recess39 a is of a substantially triangular shape in this embodiment. Therecess 39 a is provided in a female coupling shaft 39 b which isintegral with a gear 43 in the main assembly 14 of the apparatus. Thefemale coupling shaft 39 h is rotatable and movable in the axialdirection relative to the main assembly 14 of the apparatus. With thisstructure of this example, when the process cartridge B is mounted tothe main assembly 14 of the apparatus, the projection 37 a enters therecess 39 a provided in the main assembly 14 (FIG. 40 (a)). When therecess 39 a starts to rotate, the recess 39 a and the projection 37 aare brought into engagement with each other. When the rotating force ofthe recess 39 a is transmitted to the projection 37 a, the edge lines 37a 2 of the substantially equilateral triangle projection 37 a and theinner surfaces 39 a 2 of the recess 39 a, are uniformly contacted toeach other, and therefore, the axes are aligned (FIG. 4(b)). Toaccomplish this, the diameter of the circumscribed circle R0 of the malecoupling projection 37 a is larger than that of the inscribed circle R1of the female coupling recess 39 a, and is smaller than that of thecircumscribed circle R2 of the female coupling recess 39 a. The twistingproduces such a force that projection 37 a is pulled toward the recess39 a, so that end surface of the projection 37 a 1 is abutted to thebottom 39 a 1 of the recess 39 a Thus, a thrust force is produced tourge the drum gear 7 b in the direction of an arrow d, and therefore,the photosensitive drum 7 integral with the projection 37 a is stablypositioned in the main assembly 14 of the image forming apparatus bothin the axial direction and in the radial direction.

In this example, the twisting direction of the projection 37 a isopposite from the rotational direction of the photosensitive drum 7 inthe direction from the bottom trunk of the projection 37 a toward thefree end thereof, as seen from the photosensitive drum 7; the twistingdirection of the recess 39 a is opposite in the direction from the inletof the recess 39 a toward the inside; and the twisting direction of thedrum gear 7 b of the drum flange 36 is opposite from the twistingdirection of the projection 37 a.

The male shaft 37 and the projection 37 a are provided on the drumflange 36 such that when the drum flange 36 is mounted to end of thephotosensitive drum 7, they are coaxial with the axis of thephotosensitive drum 7. Designated by 36 b is an engaging portion whichis engaged with the inner surface of the drum cylinder 7 d when the drumflange 36 is mounted to the photosensitive drum 7. The drum flange 36 ismounted to the photosensitive drum 7 by crimping or bonding. Thecircumference of the drum cylinder 7 d is coated with a photosensitivelayer 7 e.

As described hereinbefore, the process cartridge B of this embodiment isas follows:

A process cartridge detachably mountable to a main assembly of anforming apparatus 14, wherein said main assembly includes a motor 61, amain assembly side gear 43 for receiving driving force from said motor61 and a hole 39 a defined by twisted surfaces, said hole 39 a beingsubstantially coaxial with said gear 43; an electrophotographicphotosensitive drum 7;

process means (8, 9, 10) actable on said photosensitive drum 7; and

a twisted projection 37 engageable with said twisted surfaces, saidprojection 37 being provided at a longitudinal end of saidphotosensitive drum 7, wherein when said main assembly side gear 43rotates with said hole 39 a and projection 37 engaged with each other,rotational driving force is transmitted from said gear 43 to saidphotosensitive drum 7 through engagement between said hole 39 a and saidprojection 37.

The twisted projection 37 is provided at a longitudinal end of saidphotosensitive drum 7, and has a non-circular cross-section andsubstantially coaxial with a rotation axis of said photosensitive drum7, wherein said projection 37 of said photosensitive drum 7 has such adimension and configuration that it can take a first relative rotationalposition with respect to a recess 39 a of the driving rotatable member(main assembly side gear 43) in which relative rotational movementtherebetween is permitted, and a second relative rotational positionwith respect to said recess 39 a of said driving rotatable member inwhich relative rotational movement is prevented in one rotationaldirection, while the rotation axis of said driving rotatable member andthe rotation axis of said photosensitive drum 7 are substantiallyaligned.

As described in the foregoing, a spur gear 7 n is fixed to the otherend-of the photosensitive drum 7.

Examples of the material of the spur gear 7 n and the drum flange 36include polyacetal, polycarbonate, polyamide and polybutyleneterephthalate or another resin material. However, another material isusable.

Around the projection 37 a of the male coupling shaft 37 of the processcartridge B, there is provided a cylindrical projection 38 a(cylindrical guide 13 aR) coaxial with the male shaft 37, whichprojection 38 a is integral with a bearing 38 fixed to a cleaning frame13. The projection 37 a of the male coupling shaft 37 is protected when,for example, the process cartridge B is mounted or demounted, andtherefore, it is not damaged or deformed. Thus, the possible play orvibration during driving through the coupling due to damage of theprojection 37 a, can be prevented.

The bearing 38 may function as a guiding member when the processcartridge B is mounted or demounted relative to the main assembly 14 ofthe image forming apparatus. More particularly, when the processcartridge B is mounted to the main assembly 14 of the image formingapparatus, the projection 38 a of the bearing 38 and the side guideportion 16 c of the main assembly are contacted, and the projection 38 afunctions to position the process cartridge B to the mounting position(guide 13 aR) to facilitate the mounting and demounting of the processcartridge B relative to the main assembly 14 of the apparatus. When theprocess cartridge B is mounted to the mounting position, the projection38 a is supported by a positioning groove 16 d formed in the guideportion 16 c.

Among the photosensitive drum 7, drum flange 36 and the male couplingshaft 37, there is a relation shown in FIG. 11. More particularly,H>F≧M, and E>N,

where H is an outer diameter of the photosensitive drum 7; E is circlediameter of a dedendum of the drum gear 7 b; F is a diameter of thebearing of the photosensitive drum 7 (an outer diameter of the shaftportion of the male coupling shaft 37, and an inner diameter of thebearing 38); M is a circumscribed circle diameter of the male couplingprojection 37 a; and N is a diameter of the engaging portion between thephotosensitive drum 7 and the drum flange 36 (the inner diameter of thedrum).

By H>F, the sliding load torque at the bearing portion can be reducedthan when the drum cylinder 7 d is born; by F>M, the mold structure canbe simplified since no undercut portion is provided, in view of the factthat when the flange portion is molded, the mold is divided normally inthe direction of a direction of arrow p in the Figure.

By E>N, the mold configuration of the gear portion is formed above theleft mold as seen in the direction of mounting of the process cartridgeB, and therefore, the right-hand mold can be simplified to improve thedurability of the mold.

The main assembly 14 of the image forming apparatus is provided withcoupling means of the main assembly. The coupling means of the mainassembly has the female coupling shaft 39 b (circular columnconfiguration) at a position aligned with the rotation axis of thephotosensitive drum when the process cartridge B is inserted (FIG. 11,25). The female coupling shaft 39 b, as shown in FIG. 11, is a drivingshaft integral with the large gear 43 for transmitting the driving forceto the photosensitive drum 7 from the motor 61. The female shaft 39 b isprojected from the lateral edge of the large gear 43 at the center ofrotation of the large gear 43. In this example, the large gear 43 andthe female coupling shaft 39 b are integrally molded.

The large gear 43 in the main assembly 14 is a helical gear, which is inmeshing engagement with a small helical gear 62 fixed to or integralwith the shaft 61 a of the motor 61; the twisting directions and theinclination angles thereof are such that when the driving force istransmitted from the small gear 62, female shaft 39 b is moved towardthe male shaft 37 by the thrust force produced. Thus, when the motor 61is driven for image formation, the female shaft 39 b is moved toward themale shaft 37 by the thrust force to establish engagement between therecess 39 a and the projection 37 a. The recess 39 a is provided at theend of the female shaft 39 b in alignment with the center of rotation ofthe female shaft 39 b.

In this embodiment, the driving force is directly transmitted from thesmall gear 62 of the motor shaft 61 a to the large gear 43, but it maybe transmitted through a speed reduction gear train, belt-pulley means,a couple of friction rollers, a combination of a timing belt and apulley.

Referring to FIGS. 24 and 27 to 29, a description will be made as to astructure for engaging the recess 39 a and the projection 37 a ininterrelation with the closing operation of the openable cover 35.

As shown in FIG. 29, the larger gear 43 is between the side plate 67 andthe side plate 66 in the main assembly 14, and the female coupling shaft39 b coaxially integral with the large gear 43 is rotatably supported bythe side plates 66, 67. An outer cam 63 and an inner cam 64 are closelyinserted between the large gear 43 and the side plate 66. The inner cam64 is fixed to the side plate 66, and the outer cam 63 is rotatablyengaged with the female coupling shaft 39 b. The surfaces of the outercam 63 and the inner cam 64 which are substantially perpendicular to theaxial direction and which are faced to each other, are cam surfaces, andare screw surfaces coaxial with the female coupling shaft 39 b and arecontacted to each other. Between the large gear 43 and the side plate67, a compression coil spring 68 is compressed and fitted around thefemale coupling shaft 39 b.

As shown in FIG. 27, an arm 63 a is extended from an outer periphery ofthe outer cam 63 in a radial direction, and an end of the arm 63 a iscoupled with an end of a link 65 by a pin 65 b at a position oppositefrom the openable cover 35. The other end of the link 65 is coupled tothe cover 35 by a pin 65 a.

FIG. 28 is a view as seen from the right in FIG. 27, and when theopenable cover 35 is closed, the link 65, outer cam 63 and the like areat the positions shown in the figure, where the male coupling projection37 a and the recess 39 a are engaged so that driving force can betransmitted from the large gear 43 to the photosensitive drum 7. Whenthe openable cover 35 is opened, the pin 65 a is rotated upward aboutthe fulcrum 35 a, so that arm 63 a is pulled up through the link 65, andthe outer cam 63 is rotated; thus, relative sliding motion is causedbetween the outer cam 63 and the inner cam 64 to move the large gear 43away from the photosensitive drum 7. At this time, the large gear 43 ispushed by the outer cam 63, and is moved against the compression coilspring 68 mounted between the side plate 67 and the large gear 43, bywhich the female coupling recess 39 a is disengaged from the malecoupling projection 37 a as shown in FIG. 29 to release the coupling tobring the process cartridge B into demountable state.

On the contrary, when the openable cover 35 is closed, the pin 65 aconnecting the link 65 with the openable cover 35, is rotated downwardabout the fulcrum 35 a, and the link 65 is moved downward to push thearm 63 a down, so that outer cam 63 is rotated in the oppositedirection, by which the large gear 43 is moved to the left by the spring68 to a position shown in FIG. 28, so that large gear 43 is set again ata position of FIG. 28, and the female coupling recess 39 a is engagedwith the male coupling projection 37 a to re-establish a drivetransmittable state. Thus, the demountable state and the drivetransmittable state of the process cartridge B are established inresponse to opening and closing of the openable cover 35. When the outercam 63 is rotated in the opposite direction by the closing of theopenable cover 35 to move the large gear 43 to the left from theposition of FIG. 29, the female coupling shaft 39 b and the end surfaceof the male coupling shaft 37 may be abutted to each other so that malecoupling projection 37 a and the female coupling recess 39 a may not beengaged with each other. However, they will be brought into engagementas soon as starting of the image forming apparatus A, as will bedescribed hereinafter.

Thus, in this embodiment, as the process cartridge B is mounted to ordemounted from the main assembly 14 of the apparatus, the openable cover35 is opened. In interrelation with the opening and closing of theopenable cover 35, the female coupling recess 39 a is moved in thehorizontal direction (the direction of arrow j). As the processcartridge B is mounted to or demounted from the main assembly 14, thecoupling (37 a, 39 a) of the main assembly 14 and the process cartridgeB are not to be engaged. And, they should not be engaged. Thus, themounting and demounting of the process cartridge B relative to the mainassembly 14 can be carried out smoothly. In this example, the femalecoupling recess 39 a is urged toward the process cartridge B by thelarge gear 43 being urged by the compression coil spring 68. When themale coupling projection 37 a and the recess 39 a are initially broughtinto engagement, they may abut each other, and therefore, they are notproperly engaged. When, however, the motor 61 is first rotated after theprocess cartridge B is mounted to the main assembly 14, the femalecoupling recess 39 a is rotated, permitting the projection 37 a and therecess 39 a to be brought into engagement.

A description will now be made as to the configurations of theprojection 37 a and the recess 39 a constituting the engaging portion ofthe coupling means.

The female coupling shaft 39 b provided in the main assembly 14 ismovable in the axial direction, as described hereinbefore, but it notmovable in the radial direction. The process cartridge B is movable inits longitudinal direction and the cartridge mounting direction (xdirection (FIG. 9)) when it is mounted in the main assembly. In thelongitudinal direction, the process cartridge B is permitted to movebetween the guiding members 16R, 16L provided in the cartridge mountingspace S.

When the process cartridge B is mounted to the main assembly 14, aportion of a cylindrical guide 13 aL (FIG. 6, 7 and FIG. 9) formed onthe flange 29 mounted to the longitudinal end of the cleaning frame 13,is fitted substantially without gap into the positioning groove 16 b(FIG. 9) of the main assembly 14 to accomplish correct positioning, andthe spur gear 7 n fixed to the photosensitive drum 7 is brought intomeshing engagement with a gear (unshown) for transmitting the drivingforce to the transfer roller 4. On the other hand, at the otherlongitudinal end (driving side) of the photosensitive drum 7, acylindrical guide 13 aR formed on the cleaning frame 13, is supported bya positioning groove 16 d provided in the main assembly 14.

By the cylindrical guide 13 aR being supported in the positioning groove16 d of the main assembly 14, the drum shaft 7 a and the female shaft 39b are aligned with the deviation not more than 2.00 mm, so that firstaligning function in the coupling action process is accomplished.

By closing the openable cover 35, the female coupling recess 39 a ismoved horizontally to enter the projection 37 a.

Then, at the driving side (coupling side), the positioning and the drivetransmission are carried out as follows.

When the driving motor 61 of the main assembly 14 is rotated, the femalecoupling shaft 39 b is moved toward the male coupling shaft 37 (thedirection opposite from the direction of arrow d in FIG. 11), and whenthe phase alignment is reached between the male coupling projection 37 aand the recess 39 a (in this embodiment, the projection 37 a and therecess 39 a have substantially equilateral triangle configurations, thephase alignment is reach at each 120 degrees of rotation), they arebrought into engagement, so that rotating force is transmitted to theprocess cartridge B from the main assembly 14 (from the state shown inFIG. 29 to the state shown in FIG. 28).

The sizes of the equilateral triangles of the male coupling projection37 a and the recess 39 a are different; more particularly, thecross-section of the triangular recess of the female coupling recess 39a is larger than the cross-section of the triangular projection of themale coupling projection 37 a, and therefore, they are smoothly boughtinto engagement.

The lower limit of the inscribed circle diameter of the triangular shapeof the projection is about 8.0 mm from the standpoint of the necessaryrigidity, and in this embodiment, it is 8.5 mm, and the inscribed circlediameter of the triangular shape of the recess is 9.5 mm, so that thegap is 0.5 mm.

In order to establish engagement of coupling with a small gap, it isdesirable to establish a certain degree of alignment before theengagement.

In this embodiment, in order to provide the concentricity of 1.0 mmdesirable for the engagement with the gap of 0.5 mm, the projectionlength of the projection 38 of the cylindrical bearing is made longerthan the projection length of the male coupling projection 37 a, and theoutside circumference of the female shaft 39 a is guided by more thantwo projected guides 13 aR4 provided in the projection 38 a of thebearing, by which the concentricity before the coupling engagementbetween the projection 37 and the female shaft 39 a is maintained atless than 1.0 mm, so as to stabilize the engaging action of the coupling(second aligning function).

When the image forming operation is started, the female coupling shaft39 b is rotated while the male coupling projection 37 a is in the recess39 a, the inner surfaces of the female coupling recess 39 a are broughtinto abutment to the three edge lines of the substantially equilateraltriangular prism of the projection 37 a, so that driving force istransmitted. At this time, the male coupling shaft 37 is moved to bealigned with the female shaft 39 b such that inner surfaces of thefemale coupling recess 39 a of the regular prism are uniformly contactedto the edge lines of the projection 37 a.

Thus, the alignment between the male coupling shaft 37 and the femaleshaft 39 b, are automatically established by the actuation of the motor61. By the driving force transmitted to the photosensitive drum 7, theprocess cartridge B tends to rotate, by which a regulating abutment 13 j(FIGS. 4, 5, FIGS. 6, 7 and FIG. 30) formed on the upper surface of thecleaning frame 13 of the process cartridge B, is urged to the fixingmember 25 (FIGS. 9, 10 and FIG. 30) fixed to the main assembly 14 of theimage forming apparatus, thus correctly positioning the processcartridge B relative to the main assembly 14.

When the driving is not effected (image forming operation is not carriedout), the gap is provided in the radial direction between the malecoupling projection 37 a and the recess 39 a, so that engagement anddisengagement of the coupling are easy. When the driving is effected,the urging force is provided with stabilization, so that play orvibration there can be suppressed.

In this embodiment, the male coupling projection and recess havesubstantially equilateral triangle shapes, but the same effects can beprovided when they are substantially regular polygonal in configuration.Substantially regular polygonal configuration is desirable since thenthe positioning can be effected with high precision, but this is notlimiting, and another polygonal shape is usable if the engagement isestablished with axial force. The male coupling projection may be in theform of a male screw having a large lead, and the female coupling recessmay be in the form of a complementary female screw. In such a case,triangle male and female screws having three leads corresponds theforegoing male coupling projection and female recess.

When the male coupling projection and the female recess are compared,the projection is more easily damaged, and has poorer mechanicalstrength. In view of this, this embodiment is such that male couplingprojection is provided in the exchangeable process cartridge B, and thefemale coupling recess is provided in the main assembly 14 of the imageforming apparatus which is required to have a higher durability than theprocess cartridge. However, the process cartridge B may have a recess,and the main assembly may have the projection, correspondingly.

FIG. 33 is a perspective view showing in detail the mounting relationbetween the right-hand guiding member 13R and the cleaning frame 13;FIG. 34 is a longitudinal sectional view wherein the right hand guidingmember 13R is mounted to the cleaning frame 13; and FIG. 35 shows a partof a right side of the cleaning frame 13. FIG. 35 is a side view showingan outline of a mounting portion of the bearing 38 integrally formedwith the right-hand guiding member 13R.

The description will be made as to the mounting to the cleaning frame 13shown in FIG. 11 illustrating the right-hand guiding member 13R (38)having the integral bearing 38, and as to the mounting of thephotosensitive drum 7 to the cleaning frame 13.

A rear surface of the right-hand guiding member 13R has the integralbearing 38 concentric with the cylindrical guide 13 aR and having asmall diameter, as shown in FIGS. 33, 34. The bearing 38 is extended toa cylindrical end thereof through a disk member 13 aR3 provided at anaxially (longitudinally) middle portion of the cylindrical guide 13 aR.Between the bearing 38 and the cylindrical guide 13 aR, a circulargroove 38 aR4 open to inside of the cleaning frame 13, is formed.

As shown in FIGS. 33-35, a side surface of the cleaning frame 13 isprovided with a partly circular-cylindrical shaped hole 13 h forreceiving the bearing, and the gap portion 13 h 1 has faced end portionswith a gap therebetween smaller than the diameter of the bearingmounting hole 13 h and larger than the diameter of the couplingprojected shaft 37. Since the coupling projected shaft 37 is engagedwith the bearing 38, it is spaced from the bearing mounting hole 13 h. Apositioning pin 13 h 2 is formed integrally on the side surface of thecleaning frame 13, and is fitted closely into the flange 13 aR1 of theguiding member 13R. By dosing so, the photosensitive drum 7 in the formof an unit can be mounted to the cleaning frame 13 in a transversedirection crossing with the axial direction (longitudinal direction),and the position of the right-hand guiding member 13R is correctlydetermined relative to the cleaning frame when the right-hand guidingmember 13R is mounted to the cleaning frame 13 in the longitudinaldirection.

When the photosensitive drum 7 unit is to be mounted to the cleaningframe 13, the photosensitive drum 7 unit is moved in the directioncrossing with the longitudinal direction, as shown in FIG. 33, to insertit into the bearing mounting hole 13 h while moving the male couplingshaft 37 through the gap portion 13 h 1 with the drum gear 7 b beinginside the cleaning frame 13. With this state, the drum shaft 7 aintegral with the left-hand guide 13 aL shown in FIG. 11 is insertedthrough a lateral edge 13 k of the cleaning frame 13 to be engaged withthe spur gear 7 n, and a small screw 13 d is threaded through the flange29 of the guide 13 aL into the cleaning frame 13, thus fixing the guide13 aL to the cleaning frame to support one end portion of thephotosensitive drum 7.

Then, the outer periphery of the bearing 38 integral with the right-handguiding member 13R, is fitted into the bearing mounting hole 13 h, andthe inner circumference of the bearing 38 is engaged with the malecoupling shaft 37; and then, the positioning pin 13 h 2 is fitted intothe hole of the flange 13 aR1 of the right-hand guiding member 13R.Then, a small screw 13 aR2 is threaded through the flange 13 aR1 intothe cleaning frame 13, thus fixing the right-hand guiding member 13R tothe cleaning frame 13.

In this manner, the photosensitive drum 7 is correctly and securelyfixed to the cleaning frame 13. Since the photosensitive drum 7 ismounted to the cleaning frame 13 in the direction transverse to thelongitudinal direction, the longitudinal end structures are simplified,and the longitudinal dimension of the cleaning frame 13 can be reduced.Therefore, the main assembly 14 of the image forming apparatus can bedownsized. The cylindrical guide 13 aL has the large flange 29 securelyabutted to the cleaning frame 13, the drum shaft 7 a integral with theflange 29 is closely fitted into the cleaning frame 13. The right-handside cylindrical guide 13 aR is coaxial with and integral with thebearing 38 supporting the photosensitive drum 7. The bearing 38 isenlarged into the bearing mounting hole 13 h of the cleaning frame 13,and therefore, the photosensitive drum 7 can be positioned correctlyperpendicularly to the feeding direction of the recording material 2.

The left side cylindrical guide 13 aL, the large area flange 29 and thedrum shaft 7 a projected from the flange 29, are of integral metal, andtherefore, the position of the drum shaft 7 a is correct, and thedurability is improved. The cylindrical guide 13 aL is not worn even ifthe process cartridge B is repeatedly mounted to or demounted from themain assembly 14 of the image forming apparatus. As describedhereinbefore in connection with the electric contacts, the electricalground of the photosensitive drum 7 is easy. The right-hand sidecylindrical guide 13 aR has a larger diameter than the bearing 38, andthe bearing 38 and the cylindrical guide 13 aR are coupled by a diskmember 13 aR3. The cylindrical guide 13 aR is coupled with the flange 13aR1, and therefore, the cylindrical guide 13 aR and the bearing 38 arereinforced and stiffened each other. Since the right-hand cylindricalguide 13 aR has a large diameter, it has enough durability against therepeated mounting-and-demounting of the process cartridge B relative tothe image forming apparatus, although it is made of synthetic resinmaterial.

FIGS. 36 and 37 illustrate another mounting method of the bearing 38integral with the right-hand guiding member 13R to the cleaning frame13.

These are schematic views and show the bearing 38 of the photosensitivedrum 7 as a major part.

As shown in FIG. 36, there is provided a rib 13 h 3 extendedcircumferential at the outside edge of the bearing mounting hole 13 h,and the outer periphery of the rib 133 h 3 is a partial cylindricalconfiguration. In this example, a portion of the right-hand cylindricalguide 13 aR extended beyond the disk member 13 aR3 to the flange 13 aR1,is closely fitted around the outer periphery of the rib 13 h 3. Thebearing mounting portion 13 h of the bearing 38 and the outer peripheryof the bearing 38 are loosely fitted. With this structure, although thebearing mounting portion 13 h is non-continuous because of the gapportion 13 h 1, the opening of the gap portion 13 h 1 can be prevented.

For the same purpose, a plurality of confining bosses 13 h 4 may beprovided at the outer periphery of the rib 13 b 3, as shown in FIG. 34.

The confining boss 13 h 4 is manufactured by metal mold with thefollowing accuracy, for example; IT tolerance of 9 the grade for thecircumscribed circle diameter, and the concentricity of −0.01 mm or lessrelative to the inside circumference of the mounting hole 13 h.

When the drum bearing 38 is mounted to the cleaning frame 13, an innerperipheral surface 13 aR5 of the drum bearing 38 opposed to the outsidecircumference confines the confining boss 13 h 4 of the cleaning frame13, while the mounting hole 13 h of the cleaning frame 13 and theoutside circumference of the bearing 38 are engaged, so that possiblemisalignment during assembling due to the opening of the gap portion 13h 1 can be prevented.

(Structure for Connecting Cleaning Chamber Frame (Drum Chamber Frame)and Image Developing Chamber Frame)

As stated previously, the cleaning chamber frame 13 and image developingchamber frame 12 of the process cartridge B are united after thecharging roller 8 and the cleaning means 10 are assembled into thecleaning chamber frame 13 and the developing means 9 is assembled intothe image developing chamber frame 12.

The essential characteristics of the structure which units the drumchamber frame 13 and the image developing chamber frame 12 will bedescribed below with reference to FIGS. 12, 13 and 32. In the followingdescription, “right-hand side and left-hand side” means the right-handside and left-hand side as seen from above, with reference to thedirection in which the recording medium 2 is conveyed.

The process cartridge removably installable in the main assembly 14 ofan electrophotographic image forming apparatus comprises: anelectrophotographic photosensitive drum 7; a developing means 9 fordeveloping a latent image formed on the electrophotographicphotosensitive drum 7; an image developing chamber frame 12 whichsupports the developing means 9; a drum chamber frame 13 which supportsthe electrophotographic photosensitive drum 7; a toner chamber frame 11which houses toner storing portion; a compression type coil spring, oneend of which is attached to the image developing chamber frame 12, beinglocated above one of the lengthwise ends of the developing means, andthe other end of which is in contact with the drum chamber frame 13; afirst projection (right-hand side arm portion 19) which is projectingfrom the image developing chamber frame 12 in the directionperpendicular to the lengthwise direction of the developing means 9,being located above the lengthwise end of the developing means 9; asecond projection (left-hand side arm portion 19); a first hole(right-hand side hole 20) of the first projection; a second hole(left-hand side hole 20) of the second projection; a first joint portion(recessed portion 21 on the right-hand side) which is located in theright-hand side lengthwise end of the drum chamber frame 13, above theelectrophotographic photosensitive drum 7, and engages with the firstprojection (arm portion 19 on the right-hand side); a second jointportion (recessed portion 21 on the left-hand side) which is located inthe left-hand side lengthwise end of the drum chamber frame 13, abovethe photosensitive drum 7, and is engaged with the second projection(arm portion 19 on the left-hand side); a third hole (hole 13 eillustrated on the right-hand side in FIG. 12) of the first jointportion (recessed portion 21 on the right-hand side); a fourth hole(hole 13 e illustrated on the left-hand side in FIG. 12) of the secondjoint portion (recessed portion 21 on the left-hand side); a firstpenetration member (joining member 22 on the right-hand side in FIG. 12)which is put through the first hole (right hole 20 and the third hole(right hole 13 e), with the first projection (right arm portion 19) andthe first joint portion (right recessed portion 21) being engaged witheach other, to connect the drum chamber frame 13 and the imagedeveloping chamber frame 12; a second penetrating member (joining member22 on the left-hand side in FIG. 12) which is put through the secondhole (left hole 20) and the fourth hole (left hole 13 e), with thesecond projection (left arm portion 19) and the second joint portion(left recessed portion 21) being engaged with each other, to connect thedrum chamber frame 13 and the image developing chamber frame 12.

The image developing chamber frame 12 and drum chamber frame 13 of theprocess cartridge B, which are structured as described above, are joinedthrough the following steps: the first joining step for joining thefirst projection (right arm portion 19) of the image developing chamberframe 12 and the first joint portion (right recessed portion 21) of thedrum chamber frame 13; the second joining step for joining the secondprojection (left arm portion 19) and the second joint portion (leftrecessed portion 21); the first penetrating step for putting the firstpenetrating member (right joining member 22) through the first hole(right hole 20) of the first projection (right arm portion 19) and thethird hole (right hole 13 e) of the first joint portion (right recessedportion 21), with the first projection (right arm portion 19) and thefirst joint portion (right recessed portion 21) being engaged with eachother, to connect the drum chamber frame 13 and the image developingchamber frame 12; the second penetrating step for putting the secondpenetrating member (left joining member 22) through the second hole(left hole 20) of the second projection (left arm portion 19) and thefourth hole (left hole 13 e) of the second joint portion (left recessedportion 21), with the second projection (left arm portion 19) and thesecond joint portion (left recessed portion 21) being engaged with eachother, to connect the image developing chamber frame 12 and the drumchamber frame 13. After being joined with each other through the abovedescribed steps, the image developing chamber frame 12 and the drumchamber frame 13 together constitute the process cartridge B.

According to this embodiment, the image developing chamber frame 12 andthe drum chamber frame 13 can be easily joined simply putting thejoining members 22 through their connective portions, and also can beeasily separated simply by pulling the joining members 22 out, as isevident from the above description.

Among the above described steps, the developing means 9 comprises thedeveloping roller 9 c in advance, and the first joining step for joiningthe first projection and the first joint portion, and the second joiningstep for joining the second projection and the second joint portion, arecarried out at the same time, wherein

(1) the photosensitive drum 7 and the developing roller 9 c are held inparallel;

(2) the developing roller 9 c is moved along the peripheral surface ofthe photosensitive drum 7;

(3) the image developing chamber frame 12 is rotatively moved as thedeveloping roller 9 c is moved:

(4) the first and second projections (arm portions 19 on the right- andleft-hand sides) enter the first and second joint portions (recesses 21on the right- and left-hand sides) due to the rotative movement of theimage developing chamber frame 12;

(5) the first and second projections (both arm portions 19) fully engagewith the first and second joint portions (both recessed portions 21).

With the above steps being strictly followed, the arm portion 19 can bemoved toward the recessed portion 21 by circularly moving the developingroller 9 c along the peripheral surface of the photosensitive drum 7,with lengthwise ends of the photosensitive drum 7 having been alreadyfitted with the spacer roller 9 i. Thus, the point at which the armportion 19 and the recessed portion 21 join becomes fixed. Therefore,the configuration of the arm portion 19 and the recessed portion 21 canbe designed to make it easier to align the holes 20 of the arm portion119 of the image developing chamber frame 12 and the holes 13 e of bothside walls of the recessed portion 21.

As stated previously, it is common practice to unite the imagedeveloping unit D and the cleaning unit C after the image developingunit D is formed by joining the toner chamber frame 11 and imagedeveloping chamber frame 12, and the cleaning chamber frame 13 and thecharging roller 8 are assembled into the cleaning unit C.

The image developing chamber frame 12 and the drum chamber frame 13 aredesigned so that the holes 20 of the first and second projections,respectively, and the holes 13 e of the first and second joint portions,respectively, become substantially aligned as the image developingchamber frame 12 and the drum chamber frame 13 are placed in contactwith each other following the steps described above.

Referring to FIG. 32, the profile of the tip 19 a of the arm portion 19forms an arc whose center coincides with the center of the hole 20, andthe profile of the bottom portion 21 a of the recessed portion 21 formsan arc whose center coincides with the center of the hole 13 e. Theradius of the arc-shaped portion of the tip 19 a of the arm portion 19is slightly smaller than the radius of the arc-shaped bottom portion 21a of the recessed portion 21. This slight difference in radius betweenthe arm portion 19 and the recessed portion 21 is such that when thebottom 21 a of the recess is placed in contact with the tip 19 a of thearm portion 19, the joining member 22 with a chambered tip can be easilyput through the hole 13 e of the drum chamber frame 13 (cleaning chamberframe 13) and then inserted into the hole 20 of the arm portion 19 a. Asthe joining member 22 is inserted, an arc-shaped gap is formed betweenthe tip 19 of the arm portion 19 and the bottom 21 a of the recessedportion 21, and, the arm portion 19 is rotatively supported by thejoining member 22. The gap g in FIG. 32 is exaggerated for ease ofdepiction, but the actual gap g is smaller than the size of the camberedportion of the tip of the joining member 22 or the size of the camberededge of the hole 20.

Also referring to FIG. 32, when the image developing chamber frame 12and drum chamber frame 13 are joined, they are moved so that the hole 20of the arm portion 19 forms a locus RL1 or RL2, or a locus which fallsbetween the loci RL1 and RL2. The interior surface 20 a of the top wallof the recessed portion 21 is angled so that the compression type coilspring 22 a is gradually compressed as the image developing chamberframe 12 and drum chamber frame 13 are moved toward each other asdescribed above. In other words, the image developing chamber frame 12and the drum chamber frame 13 are shaped so that as they are movedtoward each other as described above, the distance between the portionof the image developing chamber frame 12, to which the compression typespring 22 a is attached, and the aforementioned interior surface 20 a ofthe top wall of the recessed portion 21, is gradually reduced. In thisembodiment, the top end of the compression type coil spring 22 a comesin contact with a portion 20 a 1 of the slanted interior surface 20 a inthe middle of the joining process, and after the image developingchamber frame 12 and the drum chamber frame 13 are completely joined,the compression type coil spring 22 a remains in contact with a springseat portion 20 a 2 of the slanted interior surface 20 a, whichcontinues from the slanted portion 20 a 1. The axial line of thecompression type coil spring 22 a and the plane of the spring seatportion 20 a 2 perpendicularly intersect.

Because the image developing chamber frame 12 and the drum chamber frame13 are structured as descried above, it is unnecessary to compress thecompression type coil spring 22 a with the use of a dedicatedcompression means when the image developing chamber frame 12 and thedrum chamber frame 13 are united; the spring 22 a is automaticallyplaced in a proper position to press the developing roller 9 c againstthe photosensitive drum 7. In other words, the compression type coilspring 22 a can be attached to the spring seat 12 t of the imagedeveloping chamber frame 12 before the image developing chamber frame 12and the drum chamber frame 13 are united.

The locus RL1 coincides with the circle whose center coincides with thecenter of the cross-section of the photosensitive drum 7, and the locusRL2 is substantially a straight line whose distance from the slantedsurface 20 a 1 gradually reduces from the right hand side of the drawingtoward the left-hand side.

Referring to FIG. 31, the compression type coil spring 22 a is held bythe image developing chamber frame 12. FIG. 31 is a vertical section ofthe image developing chamber frame 12, at a vertical plane passedthrough the base of the arm portion 19, in parallel to the direction Xin which the process cartridge B is inserted. The image developingchamber frame 12 has the spring holding portion 12 t which protrudesupward from the top surface of the image developing chamber frame 12.This spring holding portion 12 t comprises at least a spring holdingcylindrical base portion 12 k around which the compression type coilspring 22 a is press-fitted, and a guide portion 12 n which is given asmaller diameter than the base portion 12 k so that the compression typecoil spring 22 a can be loosely fitted around it. The height of thespring holding base portion 12 k must be greater than the height thebottommost loop of the compression type coil spring 22 a reaches whenthe compression type coil spring 22 a is in the least compressed state,and is desirable to be the height the second loop of the spring 22 areaches, or greater.

Referring to FIG. 12, the recessed portion 21 is between the externalwall 13 s of the drum chamber frame 13 and a partitioning wall 13 tlocated slightly inward of the external wall 13 s.

As regards the right-hand side recessed portion 21 of the drum chamberframe 13, which is located on the same lengthwise end of the drumchamber frame 13 as the drum gear 7 b, the inward facing surface of theexternal wall 13 s and the outward facing surface of the partitioningwall 13 t, that is, the opposing two surfaces of the recessed portion21, are perpendicular to the lengthwise direction of the drum chamberframe 13, and the arm portion 19 of the image developing chamber frame12, which is located on the same lengthwise end of the image developingchamber frame 12 as the development roller gear 9 k, exactly fitsbetween these opposing two surfaces. On the other hand, the left-handside recessed portion 21 of the drum chamber frame 13, which is locatedon the same lengthwise end of the drum chamber frame 13 as the spur gear7 n, and the arm portion 19 of the image developing chamber frame 12,which is inserted into this left-hand side recessed portion 21, looselyfit in terms of the lengthwise direction of the process cartridge B.

Therefore, the image developing chamber frame 12 and the cleaningchamber frame 13 are accurately positioned relative to each other interms of the lengthwise direction of the process cartridge B. Morespecifically, this is due to the following reasons. It is easy tomanufacture a drum chamber frame 13 having a precise distance betweenthe opposing surfaces of the recessed portion 21 located at thelengthwise end of the drum chamber frame 13, and also an imagedeveloping chamber frame 12 having an arm portion 19 with an accuratewidth. Further, even when the measurement of the image developingchamber frame 12 and cleaning chamber frame 13 in the lengthwisedirection thereof change due to their deformation caused by temperatureincrease, the distance between the opposing two surfaces of the recessedportion 21, and the width of the arm portion 19 which fits between theseopposing two surfaces, scarcely change, due to their small measurements.In addition, the recessed portion 21 located on the same side as thespur gear 7 n, and the arm portion 19 which is fitted into this recessedportion 21, are provided with a play in the lengthwise direction of theprocess cartridge B, and therefore, even if the measurements of theimage developing chamber frame 12 and cleaning chamber frame 13 in thelengthwise direction change due to thermal deformation, no stress occursbetween the image developing chamber frame 12 and the cleaning chamberframe 13 due to their thermal deformation.

(Drum Grounding Path)

Next, a drum grounding path through which the charge remaining in thephotosensitive drum 7 is discharged to the apparatus main assembly 14will be described.

In this embodiment, the photosensitive drum 7 is grounded through thedriven side.

Referring to FIG. 11, the photosensitive drum 7 comprises a drum flange34, which is solidly attached to one of the lengthwise ends of the drumcylinder 7 d, the end opposite to the driven end, a portion of theflange 34 being fitted in the drum cylinder 7 d. This drum flange 34 isrotatively supported by a drum shaft 7 a fixed to a cleaning means frame13. The material for the drum shaft 7 a does not need to be limited tometallic material; for example, it may be electrically insulativesynthetic resin.

On the other end of the drum cylinder 7 d, the drum cylinder 7 d isfitted with a drum flange 36, which is also solidly attached to the drumcylinder 7 d, with a portion thereof fitted in the drum cylinder 7 d.The flange 36 is provided with a lengthwise center hole, and anelectrically conductive member 119 is fitted in this center hole of theflange 36, being enabled to freely move in the lengthwise direction ofthe photosensitive drum 7. The electrically conductive member 119 is inthe form of a rod, and is formed of metallic material. One of thelengthwise ends of the member 119 is fixed to a grounding plate 118disposed in contact with the inward surface 36 c of the drum flange 36;one end 119 a of the conductive member 119 is put through the centerhole of the grounding plate 118 and is crimped. The grounding plate 118is formed of metallic material and has elasticity. It has projections118 a, which are located, one for one, at the edges adjacent to theinternal wall of the drum cylinder 7 d. Each projection 118 a isslightly tilted toward the driven end of the photosensitive drum 7, andbites into the internal surface 7 d 1 of the drum cylinder 7 d due tothe elasticity of the projection 118 a. With the above arrangement, theelectrically conductive member 119 is moved in the lengthwise directionthereof due to the elasticity of the grounding plate 118.

FIG. 41 is a lengthwise section of the ground contact on thephotosensitive drum side illustrated in FIG. 11, depicting the sectionaldetail thereof. FIG. 42 is an elevation of the grounding plate 118.Referring to FIG. 42, the grounding plate 118 has a pair of opposingstraight edges, and a pair of opposing curved edges, the contours ofwhich are correspondent to the contour of the internal surface of thedrum cylinder 7 d. Each of the curved edge portions of the groundingplate 118 is provided with a pair of parallel grooves 118 b, whichseparate the projections 118 a from the rest of the grounding plate 118.Each projection 118 a is slightly bent at the deepest end of the grooves118 b, that is, at the base of the projection 118 a. A referential FIG.36 h designates a dowel which projects from the inward surface 36 c ofthe drum flange 36. These dowels 36 h are fitted in the correspondingholes 118 d of the grounding plate 18 d to prevent the grounding plate118 from rotating relative to the drum flange 36. Further, the groundingplate 118 is provided with a pair of holes 118 c, which are locatedbetween the projection 118 a, and the center hole at which the inwardend 119 a of the electrically conductive shaft 119 is crimped to fix theshaft 119 and the grounding plate to each other. The hole 118 c isprovided to increase the flexibility of the grounding plate 118, aroundthe hole 118 c, so that the grounding plate 118 does not flex near thecenter hole, that is, the area adjacent to the crimped portion 119 a ofthe electrically conductive shaft 119.

The outward end, that is, the ground contact portion 119 b, of theelectrically conductive member 119, is located on the inward side of thebrim 37 a 1 of the hollow projection 37 a located on the outward end ofa male type coupler shaft portion 37. Therefore, when a processcartridge B is inserted into, or removed from, the apparatus mainassembly 14, and when the process cartridge B is handled outside theapparatus main assembly 14, the ground contact 119 b is well protected.

With the provision of the above arrangement, as the ground contact 119 bis pushed inward in the lengthwise direction thereof, the center portionof the grounding plate 118 flexes inward of the drum cylinder 7 d, sothat the ground contact 119 b is enabled to move in the axial directionthereof, even though the grounding plate 118 remains fixed to the drumcylinder 7 d by the projections 118 a located at the curved edgeportions of the grounding plate 118.

Referring to FIG. 43, the ground contact 119 b is on the axial line ofthe hollow projection 37 a (male type coupler shaft portion 37).

Next, referring to FIG. 11, on the apparatus main assembly side 14, aground contact member 123 is put through the lengthwise axial portion ofa female type coupler shaft 39 b, being solidly fixed to the female typecoupler shaft 39 b. One end of the ground contact member 123 on the mainassembly side constitutes a ground contact 123 b on the apparatus mainside which comes in contact with the ground contact 119 b on the processcartridge side. The other end of the ground contact member 123constitutes a sliding type terminal 123 a, which is placed in contactwith a free end portion of a plate spring 117 which is fixed to a steelside plate 67 of the apparatus main assembly 14 with the use of smallscrews 116. The ground contact 123 b on the main assembly side slightlyprojects above the bottom surface of the coupling recess 39 a of thecoupling end of the female type coupler shaft 39 b, simplifying amaintenance checkup. The plate spring 117 is formed of electricallyconductive material, for example, spring steel, stainless steel,phosphor bronze, beryllium, bronze, or the like.

As for the material for the electrically conductive member 119, phosphorbronze, stainless steel, plated steel, or the like are usable. As forthe material for the ground contact member 123, the same materials asthose for the electrically conductive member 119 may be employed. Itshould be noted here that when spring steel is used as the material forthe plate spring 117, phosphor bronze or beryllium bronze is desirableas the material for the sliding type terminal 123 a from the standpointof wear resistance.

As an operator closes a lid 35 of the apparatus main assembly 14 aftermounting the process cartridge B in the apparatus main assembly 14, thefemale type coupler shaft 39 b on the apparatus main assembly side movestoward the hollow projection 37 a, and couples with the projection 37 a,immediately or as soon as the female type coupler shaft 39 b begins torotate. During this coupling process, the ground contact 119 b on theprocess cartridge side comes in contact with the ground contact 123 b onthe apparatus main assembly side before the brim 37 a 1 on the processcartridge side makes contact with the bottom surface 39 a 1 of thecoupling recess 39 a of the female type coupler shaft 39 b. After makingcontact with the counterparts on the process cartridge side, the femaletype coupler shaft 39 b and the ground contact member 123 are fartheradvanced against the elastic force of the grounding plate 118 by theelastic force of a compression type coil spring 68 (FIG. 28) whichpresses the female type coupler shaft 39 b toward the male type couplershaft portion 37, until the bottom surface 39 a 1 of the coupling recess39 a of the female type coupler shaft 39 b makes contact with the brim37 a 1 of the coupling projection 37 a. Meanwhile, the elasticity of theplate spring 117 keeps the plate spring 117 in contact with the slidingtype terminal 123 a which advances with the female type coupler shaft 39b.

As the female type coupler shaft 39 b begins to rotate, the couplingrecess 39 a generates such force that keeps on thrusting the couplingprojection 37 a into the coupling recess 39 a, since the front end,relative to the inward direction, of the female type coupler shaft 39 bis regulated. Therefore, the contact between the brim 37 a 1 of thecoupling projection 37 a and the bottom surface of the coupling recess39 a is reliably maintained; the coupling between the process cartridgeside coupler shafts and the apparatus mains assembly side coupler shaftis rendered reliable. The ground contact member 123 on the apparatusmain assembly side rotates with the female type coupler shaft 39 b, andthe sliding type terminal 123 a remains in contact with the plate spring117, sliding and rubbing against the plate spring 117. The speed atwhich the sliding type terminal 123 a slides on the plate spring 117 isslow, and the sliding keeps better electrical contact between the twocomponents.

Therefore, the charge remaining in the photosensitive drum 7 can bedischarged to the side plate 67 through the electrically conductivemember 119, the ground contact member 123, and the plate spring 117.

On the other hand, as the lid 35 is opened, the female type couplershaft 39 b moves in the direction to separate from the couplingprojection 37 a. More specifically, first, the bottom surface 39 a 1 ofthe coupling recess 39 a separates from the brim 37 a 1 of the couplingprojection 37 a. Next, the electrically conductive member 119 is movedfor a short period by the resiliency of the grounding plate 118, withthe ground contact 119 b on the process cartridge B side following, thatis, remaining in contact with, the ground contact 123 b on the apparatusmain assembly 14 side, and thereafter, the ground contacts 119 b and 123b become separated. At the same time as the female type coupler shaft 39b retreats, the ground contact member 123 retracts, with the slidingtype terminal 123 a bending the spring plate 117, until the female typecoupler shaft 39 b becomes completely separated from the couplingprojection 37 a. At this point, the process cartridge B can be removedfrom the apparatus main assembly 14.

In the above described embodiment, the process cartridge B is providedwith the male type coupler shaft portion 37 with the coupling projection37 a, and the apparatus main assembly 14 is provided with the femaletype coupler shaft 39 b with the coupling recess 39 a engageable withthe coupling projection 37 a. On the contrary, in an embodiment whichwill be described next, the process cartridge B is provided with afemale type coupler portion 37 with a coupling recess 37 c having a brim37 b, and the apparatus main assembly 14 is provided with a male typecoupler shaft 39 b with a coupling projection 39 c (because a male typecoupler shaft does not have a recess, there is no portion correspondentto the coupling recess 39 a), as illustrated in FIGS. 44, 45, and 46.

The coupling recess 37 c is in the form of a twisted trigonal prism, andthe coupling projection 39 c is in the form of a twisted polygonalprism, more specifically, in the form of a twisted trigonal prism with asubstantially equilateral triangular cross section. As for the sizes ofthe coupling recess 37 c and the coupling projection 39 c, the couplingrecess 37 c is larger than the coupling projection 39 c, by such anamount that when the coupling projection 39 c is placed in the couplingrecess 37 c, the edges of the coupling projection 39 c can come incontact with the corresponding internal surfaces of the coupling recess37 c.

At the center of the end surface 39 c 1 of the coupling projection 39 c,the ground contact 123 b on the apparatus main assembly 14 side isexposed, and at the bottom surface 37 c 1 of the coupling recess 37 c,the ground contact 119 b on the process cartridge B side is exposed.Referring to FIG. 44, the ground contacts 119 b and 123 b are located atthe ends of the electrically conductive member 119 and the groundcontact member 123, respectively. As for their description, referring tothe description of FIGS. 40-43 will suffice.

(Relationship Between Coupling Means and Grounding of PhotosensitiveDrum)

The above described coupling means comprises a female type coupler shaftportion with a coupling recess in the form of a twisted prism, and amale type coupler shaft with a coupling projection in the form of atwisted prism having the same shape as the female coupling portion,wherein driving force is transmitted by coupling the female and malecoupling portions. Therefore, the driving side pulls the processcartridge 7 in the axial direction, effectively stabilizing the positionof the photosensitive drum 7, or the process cartridge B, in thelengthwise direction.

On the other hand, as for means for applying pressure to keep the groundcontacts 119 b and 123 b in contact with each other, a coupling meanswhich does not generate thrust may be employed because a compressiontype coil spring 68 which presses the male type coupler shaft 39 b(coupler shaft on the apparatus main assembly side) in the axialdirection is used.

Such a coupling means may comprise a coupling projection 37 a in theform of a polygonal prism (for example, a substantially trigonal prism),not twisted, and a coupling recess 39 a in the form of a polygonal prism(for example, a substantially trigonal prism), not twisted, wherein thecoupling projection 37 a is engaged in the coupling recess 39 a. Withthis arrangement, aligning effect is generated, but thrust is notgenerated, and yet, the ground contacts 119 b and 123 b can be kept incontact with each other by the pressure from the compression type coilspring. This relationship between the apparatus main assembly side andthe process cartridge side in terms of coupler configuration may bereversed as illustrated in FIG. 45, in which the apparatus main assemblyside has a coupling projection 39 c in the form of a polygonal prism(for example, a substantially trigonal prism), and the process cartridgeside has a coupling recess 37 c (straight hole) in the form of apolygonal prism (for example, a substantially trigonal prism). Also inthis case, aligning effect is generated, but no thrust is generated, andyet, the ground contacts 119 b and 123 b can be kept in contact witheach other by the pressure from the compression type coil spring.

In the above description of the coupling means, the coupling meansmember on the driving side, and the coupling means member on the drivenside, are either both in the twisted form, relative to the axialdirection, or both in the form which is not twisted. Such configurationof the coupling means may be optionally employed depending on apparatusdesign regarding the way the process cartridge B is installed in theapparatus main assembly 14 and/or the way the photosensitive drum 7 isattached to the process cartridge B.

For example, given that the apparatus main assembly 14 is provided witha female type coupler shaft 39 a with a coupling recess in the form of atwisted polygonal prism, in order to fix the position of the processcartridge B relative to the apparatus main assembly 14 in the axialdirection (for example, in the case of an arrangement in which acompressed compression spring is placed at one end of a processcartridge space in the apparatus main assembly 14, in alignment with theaxial line of the photosensitive drum 7, and the photosensitive drum 7is attached to the cartridge frame so that it does not move in the axialdirection relative to the cleaning means frame 13), the couplingprojection 37 a of the male type coupler shaft portion 37 may be in theform of a normal polygonal prism which couples with the coupling recess39 a.

Also, it is possible to provide the apparatus main assembly 14 with amale type coupler shaft having a coupling projection in the form of apolygonal prism, and provide the process cartridge B with a female typecoupler shaft portion having a coupling recess in the form of a normalpolygonal prism which accommodates such a coupling projection on theapparatus main assembly 14 side.

Next, a grounding method, which is usable when the photosensitive drum 7is supported by the cleaning means frame 13 differently from the way itwas supported in the preceding embodiments, will be described. Referringto FIG. 47, one end of the photosensitive drum 7 is, fitted with a drumflange 34, and the other end is fitted with a drum flange 36. Both drumflanges 34 and 36 are solidly fixed to the photosensitive drum 7. Thedrum flange 36 comprises a hollow coupler shaft portion 37 with acoupling projection 37 a. Though the internal space of this hollowcoupler shaft portion 37 with the projection, a steel through shaft 24of the photosensitive drum 7 is rotatively put by press fitting, withthe end portion 24 a of the steel through shaft 24 extending into theshaft 37 far enough to overlap with a bearing 38. The through shaft 24is also rotatively fitted in the drum flange 34 on the other side of thephotosensitive drum 7. Further, a grounding plate 118 which electricallyconnects the drum cylinder 7 d and the through shaft 24 is fixed to thedrum flange 34. The bearing 38 is fixedly supported by the cleaningmeans frame 13, and rotatively supports the coupler shaft portion 37with the coupling projection 37 a. The lengthwise end portion 24 b, thatis, the end opposite to the coupling means, of the through shaft 24 isfixedly supported by being pressed into the cylindrical guide portion 13aL of the cleaning means frame 13. Thus, the photosensitive drum 7 issupported by the cleaning means frame 13. The endmost portion of the endportion 24 a of the through shaft 24 is reduced in diameter, being putthrough the core portion of the coupling projection 37 a, and exposed atthe outward surface of the coupling projection 37 a. This exposedportion of the through shaft 24 constitutes the ground contact 119 b,which is kept in contact with the ground contact 123 b on the apparatusmain assembly 14 side by the pressure from a spring.

As a motor 61 rotates, with the coupling projection 37 a and thecoupling recess 39 a being in engagement, the male type coupler shaftportion 37 with the coupling projection 37 a rotates, along with thedrum flange 36 integral with the coupler shaft portion 37, on thestationary through shaft 24. As a result, the drum cylinder 7 d and thedrum flange 34, which are integrally joined with the drum flange 36,also rotate. The drum flange 34 rotates on the through shaft 24, and theground contacts 119 b and 123 b slide upon each other.

One end of the grounding plate 118 is attached to the internal surfaceof the drum cylinder 7 d by pressure welding, and the other end iselastically in contact with the peripheral surface of the through shaft24, and therefore, as the photosensitive drum 7 rotates, the groundingplate 118 slides on the peripheral surface of the through shaft 24.

Next, referring to FIG. 48, the grounding method in another embodimentof the photosensitive drum supporting structure in accordance with thepresent invention will be described. Also in this embodiment, one end ofthe photosensitive drum 7 is fitted with a drum flange 36, and the otherend is fitted with a drum flange 34. The drum flanges 36 and 34 arefirmly attached to the photosensitive drum 7. The drum flange 36integrally comprises a hollow male type coupler shaft portion 37 with acoupling projection 37 a. Through the internal space of this couplershaft portion 37 with the coupling projection 37 a, a steel throughshaft 24 of the photosensitive drum 7 is rotatively put by pressfitting, with the end Portion 24 a of the steel through shaft 24extending into the shaft 37 far enough to overlap with a bearing 38. Thethrough shaft 24 is also rotatively fitted in the drum flange 34 on theother side of the photosensitive drum 7. The bearing 38 is fixedlysupported by the cleaning means frame 13, and rotatively supports thecoupler shaft portion 37 with the coupling projection 37 a. Thelengthwise end portion 24 b, that is, the end opposite to the couplingmeans, of the through shaft 24 is rotatively supported by a bearing 28which is supported by being fitted into the cylindrical guide portion 13aL of the cleaning means frame 13. Thus, the photosensitive drum 7 issupported by the cleaning means frame 13.

The grounding plate 118 is fixed to a through shaft 26 of thephotosensitive drum 7, and also to the drum cylinder 7 d, with theprojections of the grounding plate 118 biting into their surfaces (FIGS.41 and 42 illustrate the projection which bites into the drum cylinder 7d, and projection which bites into the through shaft 26 is similar inshape to the projection for the drum cylinder 7 d).

Next, referring to FIG. 49, the grounding method in another embodimentof the photosensitive drum supporting structure in accordance with thepresent invention will be described. Each lengthwise end of thephotosensitive drum 7 is fitted with drum flanges 34 and 36,respectively. In this embodiment, one end of a through shaft 27 of thephotosensitive drum 7 integrally comprises a male type coupler portion37 a, and this through shaft 27 is put through the drum flanges 36 and34 by press fitting or the like method, being thereby fixed thereto. Thecoupling means side end of the through shaft 27 is increased indiameter, forming an enlarged diameter portion 27 a, and is rotativelyfitted in a bearing 38 which is supported by the cleaning means frame13. The other end 27 c of the through shaft 27 is rotatively fitted in abearing 28 which is fixedly supported by the cleaning means frame 13.Thus, the photosensitive drum 7 is supported by the cleaning means frame13.

As for the electrical connection between the through shaft 27 and thedrum cylinder 7 d, a grounding plate 118 is provided, which is formed ofspring steel, and has the same type of projections as those illustratedin FIGS. 41 and 42, which bite into the through shaft 27 and the drumcylinder 7 d in order to electrically connect the through shaft 27 andthe drum cylinder 7 d. The through shaft 27 is formed of steel orelectrically conductive resin.

As the coupling projection 37 a fits into the coupling recess 39 a onthe apparatus main assembly 14 side, the end surface 37 a 1 (groundcontact 119 b) of the coupling Projection 37 a comes in contact with theground contact member 123 on the apparatus main assembly 14 side.

As for the direction in which the coupling recess 39 a, and the couplingprojection 37 a, are twisted, it is opposite to the direction in whichthe drum gear is rotated, as seen from the entrance side of the recesslooking toward the bottom side thereof.

The amount of the twist of the recess and the projection is at a rate of1° to 15° per 1 mm of axial length.

The depth of the recess in this embodiment is approximately 4 mm, and istwisted approximately 30° overall.

Although the coupling means in the preceding embodiment comprised atwisted recess and a twisted polygonal prism, the coupling means maycomprise a twisted hole and a normal polygonal prism. In the case of thelatter, a normal trigonal prism, for example, fits into a twistedrecess, and as the recess rotates, the trigonal prism makes contact withthe internal surface of the recess by the base portion, whereby theposition of the trigonal prism is fixed relative to the recess. Thisbase portion of the trigonal prism is rendered relatively strongcompared to the other portions, and therefore, the trigonal prism as thecoupling projection does not deform in terms of overall shape. However,the edges of the trigonal prism, the adjacencies thereof, and/or theinternal surface of the recess correspondent thereto, slightly deform asthe edges and the adjacencies thereof bite into the internal wall of thehole, better stabilizing the state of the coupling between theprojection and the recess. The normal prism is easier to form than thetwisted one.

Since the coupling means in accordance with the present inventiongenerates self aligning effect, the location of the rotational center ofthe ground contact on the process cartridge B side coincides with thelocation of the ground contact on the apparatus main assembly side whichis at the center of the coupling means member on the apparatus mainassembly side. Therefore, the sweeping area of the mutually rubbingground contacts becomes smallest possible, and also the speed at whichthe ground contacts rub each other becomes slowest possible. As aresult, the lives of the ground contacts become longer, and also, thestate of the contact between the ground contacts become more stable.Further, because the contact surface on the process cartridge side isnot outwardly exposed, it is possible to prevent such contact failurethat is caused as a hand or the like comes in contact with the contactsurface.

FIG. 50 illustrates another embodiment of the photosensitive drumgrounding method in accordance with the present invention.

A ground contact member 123 on the apparatus main assembly 14 side isloosely put through the core portion of the male type coupler shaft 39 bwith a coupling projection 39 c, and is nonrotative. The outward end ofthe ground contact member 123 is fixed to a plate spring 117 bycrimping. The other features of this embodiment are the same as those inthe embodiment illustrated in FIG. 44.

FIG. 51 illustrates another embodiment of the photosensitive drumgrounding method in accordance with the present invention.

A ground contact member 123 on the apparatus main assembly 14 side isfixed to a female type coupler shaft 39 b, which is supported by abearing 116 fixed to the side plate of the apparatus main assembly 14.Between the outward end of the ground contact member 123 and the bearing116, a compression type coil spring 117 is nonrotatively attached, andtherefore, the compression type coil spring 117 and the ground contactmember 123 rub against each other. Also in this embodiment, thephotosensitive drum 7 is grounded as the ground contacts 119 b and 123 bcome in contact with each other.

In the preceding embodiments, the ground contact 119 b was disposed atthe center of the drum flange 36. In other words, the ground contact 119b is placed on the axial line of the drum flange 36. However, thiselectrically conductive member 119 can be eliminated. More specifically,the drum flange 36 is rendered solid, and electrically conductive on itsown, and is placed in contact with the ground contact member 123. As forthe material usable for such a drum flange 36, polyacetal which containselectrically conductive filler, polyphenylene sulfone which containselectrically conductive filler, polyamide which contains electricallyconductive filler, and the like material, are proper. With theelimination of the electrically conductive member 119, the structure ofthe core portion of the coupler shaft can be simplified, and therefore,the number of assembly steps can be reduced. As for the electricallyconductive filler, carbon powder, metal powder, metal coated glassfiber, and the like are usable.

FIG. 52 shows another embodiment of the photosensitive drum groundingstructure in accordance with the present invention.

The coupling means member (drum flange 36) in this embodiment is formedby two color injection molding. In other words, a coupling projection 37a, and a narrow diameter portion 36 d (dotted portion) integral with theprojection 37 a, are formed of the aforementioned electricallyconductive material, whereas a gear 7 b (helical gear) portion is formedof highly wear resistant material (for example, polyacetal orpolycarbonate). The portion designated with a referential FIG. 36 e iswhere the drum flange 36 is fitted in the drum cylinder 7 d. Accordingto this embodiment, the charge in the photosensitive drum 7 isdischarged to the apparatus main assembly 14 through the narrow diameterportion 36 d and the coupling projection 37 a.

FIG. 53 is another embodiment of the coupling projection in accordancewith the present invention. In this embodiment, a make type couplershaft portion 37 comprises a support shaft 37 a 5 and a plurality ofspherical contacts 37 a 3. The support shaft 37 a 5 is disposed on theend surface of the coupler shaft 37, and the plurality of sphericalcontacts 37 a 3 are attached, one for one, to the end of a plurality ofradial arms extending from the support shaft 37 a 5. The driving forceis transmitted as the plurality of spherical c-contacts 37 a 3 makecontact with the internal surface of the coupling recess 39 a. A groundcontact 119 b is exposed at the inward end of the support shaft 37 a 5.

FIG. 54 depicts another embodiment of the coupling projection inaccordance with the present invention. It is a modification of thecoupling projection illustrated in FIG. 53. In this modification, thecombination of the plurality of radial arms 37 a 4 and sphericalcontacts 37 a 3 in FIG. 53 are replaced with a single triangular plate37 a 4. Also in this embodiment, a ground contact 119 b is disposed onthe axial line of the coupler shaft 37.

(Another Embodiment of Grounding Method for Process Cartridge)

In this embodiment, an electrically conductive member 119 is fixed to acoupling means member 36 (drum flange), which will be described below indetail.

First, the coupling means member on the apparatus main assembly 14 sidewill be described. Referring to FIG. 55, a ground contact member 123 onthe apparatus main assembly 14 is loosely put through the core portionof the female type coupler shaft 39 b with a coupling recess 39 a, andis nonrotative, as is the ground contact member 39 b illustrated in FIG.50. The outward end of the ground contact member 123 is fixed to thefree end portion 117 a of a plate spring 117 by crimping. The otherfeatures of the coupling means structure on the apparatus main assembly14 side are the same as those of the structure illustrated in FIG. 44.

The ground contact 123 b on the apparatus main assembly 14 side projectsabove the bottom surface 39 a 1 of the coupling recess 39 a, simplifyingthe maintenance checkup. The plate spring 117 is formed of electricallyconductive material, for example, spring steel plate, stainless steelplate, phosphor bronze plate, beryllium bronze plate, or the like plate.

As for the material for the electrically conductive member 119, phosphorbronze, stainless steel, plate steel, or the like are usable. As for thematerial for the ground contact member 123, the same material as thosefor the electrically conductive member 119 are also usable, but it isdesirable that the ground contact member 123 and the electricallyconductive member 119 are different in material.

Referring to FIG. 55, a photosensitive drum 7 is fitted with a drumflange 34, which is fixedly fitted in the drum cylinder 7 d, on the sideopposite to the driven side. This drum flange 34 is rotatively supportedon a drum shaft 7 a fixed to the cleaning means frame 13. Since the drumshaft 7 a in this embodiment is not used for grounding thephotosensitive drum 7, the material therefor does not need to be limitedto metallic materials; it may be insulative synthetic resin.

On the driven side of the photosensitive drum 7, the fitting portion 36d of a drum flange 36 is fitted in the drum cylinder 7 d, and a portionof the edge of the drum cylinder 7 d is crimped into the recess 36 flocated at the peripheral surface of the fitting portion 36 d, asindicated by a referential figure K in FIG. 56A, to fix the drumcylinder 7 d and the drum flange 36 to each other. The drum flange 36has a tiered cylindrical hole 134 which comprises a portion 134 a, aportion 134 b, and a portion 134 c, which are located in this order fromthe coupling projection 37 a side. The cylindrical hole portion 134 b isslightly smaller in diameter than the cylindrical hole portion 134 a,and the cylindrical hole portion 134 c is greatly larger in diameterthan the cylindrical hole portion 134 b.

The electrically conductive member 119 is press fitted through thecentral hole 134 of the drum flange 36 fixed to the driven side or thephotosensitive drum 7, being prevented from moving in the axialdirection. This electrically conductive member 119 is a tiered rod,comprising a small diameter portion 119 d and a large diameter portion119 c. The small diameter portion 119 d is press fitted in thecylindrical hole portion 134 b, and the large diameter portion 119 c isloosely fitted in the cylindrical hole portion 134 a, with some gapbetween itself and the internal surface of the cylindrical hole portion134 a. Further, the inward end portion of the small diameter portion 119d is fitted in the central hole of a grounding plate 118, being fixedthereto. The grounding plate 118 is placed in contact with the inwardsurface of the drum flange 36. Further, the curved edges of thegrounding plate 118 are provided with a projection 118 a, the tip ofwhich slightly bends toward the driven side, and bites into the inwardsurface 7 d 1 of the drum cylinder 7 d due to its own elasticity.

FIG. 56A is an enlarged vertical section of the ground contact and theadjacencies thereof illustrated in FIG. 55, at a plane passed throughthe lengthwise axis of the photosensitive drum 7, and depicts thedetails thereof. FIG. 57 is a frontal elevation of the grounding plate118. Referring to FIG. 57, the grounding plate 118 is in the form of adisc. It has two opposing pairs of parallel slits with a predeterminedlength, which are cut from the periphery of the grounding plate 118 inparallel to any given diameter thereof, one on each side of thediameter. The portions between these parallel slits 118 b constituteprojections 118 a having an end portion 118 a 1 which is slightly benttoward the driven side. This end portion 118 a 1 has two pointed tipswhich bite into the inward surface 7 d 1 of the drum cylinder 7 d. Areferential FIG. 36 h designates a dowel which projects from the inwardsurface 36 c of the drum flange 36, and is fitted in the hole of thegrounding plate 118 to prevent the grounding plate 118 from rotatingrelative to the drum flange 36. In order to fix the grounding plate 118to the drum flange 36, after the dowel 36 h is inserted in the hole ofthe grounding plate 118, the diameter of the end portion of the dowel 36h is increased by softening it with heat. The increased diameter portionof the dowel 36 h prevents the grounding plate 118 from being separatedfrom the drum flange 36 while mounting the ground contact member 119.

A ground contact 119 b constituted of the other end of the groundcontact member 119 is located slightly inward of the brim portion 37 a 1of the hollow coupling projection 37 a of the male type coupler shaftportion 37. Therefore, when the process cartridge B is inserted into, orremoved from, the apparatus main assembly 14, and when the processcartridge B having been removed from the apparatus main assembly 14 ishandled, the ground contact 119 b is protected.

The ground contact 119 b is exposed from the bottom surface of thehollow portion of the coupling projection 37 a, below the brim portion37 a 1, on the axial line of the coupling projection 37 a, asillustrated in FIG. 41.

Next, the relationship between the grounding plate 118 and theconfiguration of the inward end 36 c of the drum flange 36 will bedescribed. Referring to FIG. 56A, the inward end 36 c of the drum flange36 is provided with a groove 36 a which extends in the diameterdirection of the drum flange 36, and is aligned with the projection 118a of the grounding plate 118 so that the bent tip portion 118 a 1 of theprojection 118 a is not prevented from biting into the inward surface of7 d 1 of the drum cylinder 7 d. The grounding plate 118 is in the formof a disc, except for the projection 118 a. The diameter of thegrounding plate 118 is slightly smaller than the internal diameter ofthe drum cylinder 7 d, and the projection 118 a slightly extends beyondthe periphery of the disk. Referring to FIG. 59, the center hole of thegrounding plate 118, in which the electrically conductive member 119 isfitted, is in the form of a letter “H,” wherein the opposing edges 118 d1 of the horizontal stroke portion which connects the left and rightvertical strokes are bent toward the nondriver side as shown in FIG. 58.The distance between these opposing edges 118 d 1 is less than thediameter of the small diameter portion 119 d of the electricallyconductive member 119

Next, regarding the grounding plate 118, the positional relationshipamong the projection 118 a, the hole 118 c in which the dowel 36 h isfitted, and the hole 118 d in which the electrically conductive member119 is fixedly fitted, will be described. The pair of opposingprojections 118 a, and the pair of opposing holes 118 c for the dowel,are located on lines (∝) and (β), respectively, which include the centerof the grounding plate 118, and each of them is located the samedistance from the center of the grounding plate 118 as is itscounterpart.

The lines (∝) and (β) intersect each other, and the angle θ between thetwo lines in this embodiment is approximately 30°. Regarding the hole118 d in which the electrically conductive member 119 is fixedly fitted,the opposing edges 118 d 1 are parallel to the line (βν), and the centerof the hole 118 d is on a line γ which is passed through the center ofthe grounding plate 118, perpendicularly to the line (βν). The distancesfrom the center of the grounding plate 118 to the opposing edges 118 d 1are equal.

The grounding plate 118 is placed in contact with the surface of theinward end 36 c of the drum flange 36, with the dowel 36 h of the drumflange 36 fitted in the hole 118 c of the grounding plate 118. Then, thehead portion of the dowel 36 h is softened with heat, and is increasedin diameter as it is rendered semispheric as shown in FIG. 56A. Then, asthe semispheric portion end portion of the dowel 36 h cools down, thedrum flange 36 and the grounding plate 118 are fixed to each other.Next, the electrically conductive member 119 is inserted in the centerhole 134 of the drum flange 36 in the direction of an arrow mark Y asshown in FIG. 56A. More specifically, first, the small diameter portion119 d of the electrically conductive member 119 is press fitted into thesmall diameter portion 134 b the center hole 134 of the drum flange 36.Next, the small diameter portion 119 d of the electrically conductivemember 119 is forced into the electrically conductive member anchoringhole 118 d located at the center of the grounding plate 118, bendinginward the opposing edges 118 d 1. Next, the large diameter portion 119c of the electrically conductive member 119 comes in contact with thestepped portion of the center hole 134 of the drum flange 36, fixing theposition of the electrically conductive member 119 relative to the drumflange 36 in the axial direction. As a result, the ground contact 119 bis located within a center hole 134, a predetermined distance inward ofthe brim portion 37 a 1 of the coupling projection 37 a.

As described above, the drum flange 36, the grounding plate 118, and theelectrically conductive member 119 are unitized as a coupling meansmember. Then, the fitting portion 36 d of the drum flange 36 is fittedin the drum cylinder 7 d, and the drum flange 36 and the drum cylinder 7d are fixed to each other as a portion of the edge of the drum cylinder7 d is crimped into the recess 36 f of the drum flange 36 as indicatedby the referential figure K. FIGS. 56B and 56C are perspective views ofthe coupling means member C illustrated in FIG. 56A.

In this embodiment, the ground contact 119 b on the cartridge side andthe ground contact 123 b on the apparatus main assembly side are placedin contact with, or separated from, each other in the following manner.As the gear 43 on the main assembly side is driven in the state depictedin FIG. 55, the photosensitive drum 7 is rotated, and the drum flange 36with a drum gear 7 b is rotated with the electrically conductive member119 (ground contact 119 b). Since the drum gear 7 b is a helical gear,it is thrust in the direction of an arrow mark d in FIG. 55. Further, aswas already described, the coupling projection 37 a and the couplingrecess 39 a pull each other in the axial direction, and therefore, thebottom surface 39 a 1 of the coupling recess 39 a and the brim 37 a 1 ofthe coupling projection 37 a are placed in contact with each other. Alsoas described before, the coupling recess 39 a is located at apredetermined position to which it is advanced as the lid 35 of theapparatus main assembly 14 is closed, and therefore, the position of thephotosensitive drum 7 relative to the axial direction is fixed.

As described above, the elastic force of the plate spring 117 pressesthe ground contact member 123 into the electrically conductive member119 of the process cartridge in the axial direction opposite to thedirection of the arrow mark d, but this elastic force is set to beweaker than both the force which works in the direction to pull thecoupling projection 37 a into the coupling recess 39 a, and the thrustgenerated by the drum gear 7 b. Therefore, the elastic force of theplate spring 117 does not interfere with the positioning of thephotosensitive drum 7 in the axial direction.

The ground contact member 123 is fixed to the plate spring 117, and isplaced in contact with the electrically conductive member 119 by theelastic force of the plate spring 117. Therefore, the ground contact 119b of the electrically conductive member 119 and the ground contact 123 bof the ground contact member 123 are kept in contact with each other,and their end surfaces slide against each other.

When the process cartridge B is removed from the apparatus main assembly14, the female type coupler shaft 39 b is retracted, together with thelarge gear 43, from the coupling projection 37 a of the male typecoupler shaft portion 37. At the beginning of the retraction of thefemale type coupler shaft 39 b, the ground contact member 123 remains incontact with the ground contact 119 b of the process cartridge B due tothe elastic force of the plate spring 117. Then, after the outward endof the female type coupler shaft 39 b comes in contact with the platespring 117, the plate spring 117 is bent leftward in FIG. 55 against itselastic force by the further retraction of the female type coupler shaft39 b. Therefore, the ground contact member 123 is pulled away; theground contact 123 b on the apparatus main assembly 14 side is separatedfrom the ground contact 119 c on the process cartridge B side. Next, thecoupling recess 39 a of the female type coupler shaft 39 b separatesfrom the coupling projection 37 a of the male type coupler shaft portion37 in the axial direction, coming out of the cylindrical projection 38 aof the bearing 38, which had surrounded the coupling projection 37 a ofthe male type coupler shaft portion 37, and stops at a predeterminedposition. This movement of the female type coupler shaft 39 b is causedby the linkage between the lid 35 and the female type coupler shaft 39 billustrated in FIGS. 27, 28 and 29.

With the female type coupler shaft 39 b retracted as described above,the process cartridge B can be installed or removed. As the lid 35 isclosed after the process cartridge B is inserted in the apparatus mainassembly 14, the female type coupler shaft 39 b advances, taking theground contact member 123 along, and the coupling recess 39 a of thefemale type coupler shaft 39 b engages with the coupling projection 37 aof the male type coupler shaft portion 37. Then, as the coupling recess39 a accepts the coupling projection 37 deeper, the ground contact 123 bon the apparatus main assembly 14 side comes in contact with the groundcontact 119 b on the cartridge side. At this point, the advance of theground contact member 123 under the pressure from the plate spring 117is stopped by the electrically conductive member 119. Then, as thefemale type coupler shaft 39 b further advances, the bottom surface 39 a1 of the coupling recess 39 a of the female type coupler shaft 39 bcomes in contact with the brim 37 a 1 of the coupling projection 37 a ofthe male type coupler shaft portion 37.

Regarding the electrically conductive member 119 and the ground contactmember 123 described in the foregoing paragraph, their materials may bethe same as those listed before. However, in this embodiment, theopposing edges 118 d 1 of the electrically conductive member anchoringhole 118 d located at the center of the grounding plate 118 must biteinto the electrically conductive member 119, and therefore, springsteel, plated spring steel, or the like, which are greater in hardnessthan the electrically conductive member 119 is desirable as the materialfor the grounding plate 118.

According to this embodiment, the electrically conductive member 119 isfixed to the drum flange 36 simply by inserting it through the centerhole of the drum flange 36, and then through the anchoring hole 118 d ofthe grounding plate 118 to prevent it from slipping out. With thisarrangement, even if the electrically conductive member 119 does not fitin the center hole 134 of the drum flange 36 as tightly as it should,the electrically conductive member 119 does not slip out of the drumflange 36. Further, the center hole 134 of the drum flange 36 has astepped portion with which the stepped portion of the electricallyconductive member 119 meets, and therefore, the electrically conductivemember 119 is accurately positioned in the axial direction, relative tothe drum flange 36.

The grounding plate 118 is fixed to the drum flange 36 by the dowel 36h, in contact with the surface of the inward end of the drum flange 36,and the projection 118 a of the grounding plate 118, which is caused tolean toward the driven side, bites into the inward surface of the drumcylinder 7 d. Therefore, the drum flange 36 is prevented from slippingout of the drum cylinder 7 d, and also, the drum cylinder 7 d isprevented from rotating relative to the drum flange 36. Further, since apart of the edge of the drum cylinder 7 d is crimped into the recess 36f of the drum flange 36, the drum flange 36 is firmly fixed to the drumcylinder 7 d.

Also, in the case of the embodiment in which the electrically conductivemember 119 is fixed to the drum flange 36, the following arrangement ispossible. That is, the center hole of the female type coupler shaft 39 bis rendered square, for example, and the ground contact member 123 whichis to be fitted in the center hole, is also rendered square, beingperfectly fitted in the square central hole, and yet, being allowed tomove freely in the axial direction. The outward end of the groundcontact member 123 is made to be a contact 123 a, which slides againstthe plate spring 117. In this case, in order to make the ground contactmember 123 retract as the female type coupler shaft 39 b is retracted,the ground contact member 123 is provided with a collar 123 c, asillustrated in FIG. 60, which is located between the female type couplershaft 39 b and the plate spring 117, and comes in contact with thefemale type coupler shaft 39 b as the female type coupler shaft 39 b isretracted.

In the preceding embodiments, the plate spring 117 was employed tocontinually press the ground contact member 123 toward the groundcontact 119 b, but a compression type coil spring 130 may be employed asillustrated in FIG. 61. In the case of the structure in FIG. 61, thecompression type coil spring 130 is placed between the outward end ofthe ground contact member 123 and a rigid side plate 131, and the groundcontact member 123 is placed in contact with the ground contact 119 b onthe cartridge side by the elastic force of the compression type coilspring 130. A reference figure 132 designates a screw, which attachesthe rigid side plate 131 to the side plate 67 of the apparatus mainassembly 14. FIGS. 25, 26, 28 and 29 illustrate the embodiment in whichthe compression type coil spring 130 is employed, but obviously, thecompression type coil spring 130 is usable with structures other thanthe above described one.

Further, the above described embodiments may be employed in combinationas needed. For example, the embodiment illustrated in FIGS. 56 and 57may be used in combination with the embodiment illustrated in FIG. 11 or61. The embodiment illustrated in FIGS. 53 and 54 may be used incombination with the embodiment illustrated in, for example, FIG. 11 or61. The embodiment illustrated in FIG. 50 may be employed in combinationwith the embodiment illustrated in FIG. 55, 60, or 61. Further, theembodiment illustrated in FIG. 52 was described with reference to themale type member of coupling means, but obviously, the embodiment isapplicable to the female type member of coupling means. The embodimentillustrated in FIG. 52 is also employable in combination with otherembodiments, for example, the coupling means member on the apparatusmain apparatus 14 side illustrated in FIG. 11, 55, 60, or 61.

As described above, according the preceding embodiments, the force fordriving a process cartridge is transmitted from the main assembly of animage forming apparatus to the process cartridge through coupling meanswhich comprises a coupler shaft on the process cartridge side and acoupler shaft on the apparatus main assembly side. The coupling end ofeither one of the coupler shafts may be provided with a hole, and thecoupling end of the other shaft is provided with a projection which fitsin the hole of the opposing coupler shaft. Further, one of the groundcontacts either on the process cartridge side or on the apparatus mainassembly side is located in the hole, and the other is located on theprojection, and therefore, an electrophotographic photosensitive drumcan be grounded through the rotative power transmitting portion locatedat one end of the drum.

According to an aspect of the present invention, the ground contacts areunder continual elastic pressure, and therefore, it is assured that theyremain in contact with each other.

According to another aspect of the present invention, the aforementionedrecess and projection are given a twisted form, and therefore, it isfurther assured that the ground contacts remain in contact each other.

According to another aspect of the present invention, the recess andprojection are given a substantially triangular cross section.Therefore, they automatically align with each other. Further, they donot need to be fit as tightly as otherwise, and therefore, they can beeasily engaged or disengaged.

In this embodiment, the process cartridge B was described as a processcartridge which forms a monochromatic image, but the present inventionis applicable, with desirable effects, to a process cartridge whichcomprises a plurality of developing means for forming an image composedof a plurality of colors (for example, two toner image, three toneimages, full color image, or the like).

The electrophotographic photosensitive member does not need to belimited to the photosensitive drum 7. For example, the following typesmay be included. First, as for the photosensitive material,photoconductive material such as amorphous silicon, amorphous selenium,zinc oxide, titanium oxide, organic photoconductor, and the like, may beincluded. As for the configuration of the base member on whichphotosensitive material is placed, it may be in the form of a drum orbelt. For example, the drum type photosensitive member comprises acylinder formed of aluminum alloy or the like, and a photoconductorlayer deposited or coated on the cylinder.

As for the image developing method, various known methods may beemployed; for example, two component magnetic brush type developingmethod, cascade type developing method, touch-down type developingmethod, cloud type developing method, and the like

Also in this embodiment, a so-called contact type charging method wasemployed, but obviously, charging means with a structure different fromthe one described in this embodiment may be employed; for example, oneof the conventional structures, in which a tungsten wire is surroundedby a metallic shield formed of aluminum or the like, on three sides, andpositive or negative ions generated by applying high voltage to thetungsten wire are transferred onto the surface of a photosensitive drumto uniformly charge the surface of the photosensitive drum.

The charging means may in the form of a blade (charge blade), a pad, ablock, a rod, a wire, or the like, in addition to being in the form of aroller.

As for the method for cleaning the toner remaining on the photosensitivedrum, a blade, a fur brush, a magnetic brush, or the like may beemployed as a structural member for the cleaning means.

As described in the foregoing, the photosensitive member can beassuredly grounded electrically.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scone of thefollowing claims.

1-73. (canceled)
 74. A process cartridge detachably mountable to a mainassembly of an electrophotographic image forming apparatus, wherein themain assembly includes a motor, a main assembly gear configured andpositioned to receive a driving force from the motor and, a twisted holehaving a non-circular cross-section and being substantially coaxial withthe gear, said process cartridge comprising: an electrophotographicphotosensitive drum; process means actable on said photosensitive drum;and a non-twisted projection which is provided at a longitudinal end ofsaid photosensitive drum and which has a base portion having anon-circular cross-section, said non-twisted projection being engageablewith the hole at the base portion, wherein when the main assembly gearrotates with the hole at the base portion, wherein when the mainassembly gear rotates with the hole and said projection engaged witheach other, a rotational driving force is transmitted from the gear tosaid photosensitive drum through engagement between the hole and thebase portion.
 75. A process cartridge according to claim 74, whereinsaid projection has a shape of a non-twisted polygonal prism.
 76. Aprocess cartridge according to claim 75, wherein the non-twistedpolygonal prism is a triangular prism.
 77. A process cartridge accordingto claim 74 or 75, wherein a rotation axis of the gear and the rotationaxis of said photosensitive drum are substantially aligned.
 78. Aprocess cartridge detachably mountable to a main assembly of anelectrophotographic image forming apparatus, wherein the main assemblyincludes a motor, a main assembly gear configured and positioned toreceive a driving force from the motor, and a twisted hole having asubstantially triangular cross section and being substantially coaxialwith the gear, said process cartridge comprising: an electrophotographicphotosensitive drum; process means actable on said photosensitive drum;and a non-twisted projection which is provided at a longitudinal end ofsaid photosensitive drum and which has a base portion having anon-circular cross section, said non-twisted projection being engageablewith the hole at three positions at the base portion, wherein when themain assembly gear rotates with the hole and said projection engagedwith each other, a rotational driving force is transmitted from the gearto said photosensitive drum through engagement between the hole and thebase portion.
 79. A process cartridge according to claim 78, whereinsaid projection has a shape of a non-twisted polygonal prism.
 80. Aprocess cartridge according to claim 79, wherein the non-twistedpolygonal prism is a triangular prism.
 81. A process cartridge accordingto claim 78, 79 or 80, wherein a rotation axis of the gear and therotation axis of said photosensitive drum are substantially aligned. 82.A process cartridge detachably mountable to a main assembly of anelectrophotographic image forming apparatus, wherein the main assemblyincludes a motor, a main assembly gear configured and positioned toreceive a driving force from the motor, a twisted hole having asubstantially triangular cross-section and being substantially coaxialwith the gear, said process cartridge comprising: an electrophotographicphotosensitive drum; process means actable on said photosensitive drum;and a non-twisted projection which is provided at a longitudinal end ofsaid photosensitive drum and which has a base portion having anon-circular cross section, said non-twisted projection being engageablewith the hole at three positions at the base portion, wherein when themain assembly gear rotates with the hole and said projection engagedwith each other, a rotational driving force is transmitted from the gearto said photosensitive drum through engagement between the hole and thebase portion, wherein said projection has a diameter of itscircumscribing circle which is larger than a diameter of an inscribingcircle of the hole and which is smaller than a diameter of acircumscribing circle of the hole such that said projection can take afirst relative rotational position with respect to the hole in whichrelative rotational movement between said projection and the hole ispermitted, and a second relative rotational position with respect to thehole in which the relative rotational movement is prevented in onedirection while the rotation axis of the gear and the rotation axis ofsaid photosensitive drum are substantially aligned.
 83. A processcartridge according to claim 82, wherein said projection has a shape ofa non-twisted polygonal prism.
 84. A process cartridge according toclaim 83, wherein the non-twisted polygonal prism is a triangular prism.85. An electrophotographic image forming apparatus comprising: a mainassembly including: a motor; a main assembly gear configured andpositioned to receive a driving force from the motor; a twisted holehaving a non-circular cross section and being substantially coaxial withthe gear; and a process cartridge detachably mounted to said mainassembly, said process cartridge including: an electrophotographicphotosensitive drum; process means actable on said photosensitive drum;and a non-twisted projection which is provided at a longitudinal end ofsaid photosensitive drum and which has a base portion having anon-circular cross-section, said non-twisted projection being engageablewith the hole at the base portion, wherein when the main assembly gearrotates with the hole and said projection engaged with each other, arotational driving force is transmitted from the gear to saidphotosensitive drum through engagement between the hole and the baseportion.
 86. An electrophotographic image forming apparatus comprising:a main assembly including: a motor; a main assembly gear configured andpositioned to receive a driving force from the motor; a twisted holehaving a substantially triangular cross-section and being substantiallycoaxial with the gear; and a process cartridge detachably mounted tosaid main assembly, said process cartridge including: anelectrophotographic photosensitive drum, process means actable on saidphotosensitive drum, and a non-twisted projection which is provided at alongitudinal end of said photosensitive drum and which has a baseportion having a non-circular cross section, said non-twisted projectionbeing engageable with the hole at three positions at the base portion,wherein when the main assembly gear rotates with the hole and saidprojection engaged with each other, a rotational driving force istransmitted from the gear to said photosensitive drum through engagementbetween the hole and the base portion.
 87. An electrophotographic imageforming apparatus comprising: a main assembly including: a motor; a mainassembly gear configured and positioned to receive a driving force fromthe motor; a twisted hole having a substantially triangularcross-section and being substantially coaxial with the gear; and aprocess cartridge detachably mounted to said main assembly, said processcartridge including: an electrophotographic photosensitive drum; processmeans actable on said photosensitive drum; and a non-twisted projectionwhich is provided at a longitudinal end of said photosensitive drum andwhich has a base portion having a non-circular cross-section, saidnon-twisted projection being engageable with the hole at three positionsat the base portion, wherein when the main assembly gear rotates withthe hole and said projection engaged with each other, a rotationaldriving force is transmitted from the gear to said photosensitive drumthrough engagement between the hole and the base portion, wherein saidprojection has a diameter of its circumscribing circle which is largerthan a diameter of an inscribing circle of the hole and which is smallerthan a diameter of a circumscribing circle of the hole such that saidprojection can take a first relative rotational position with respect tothe hole in which relative rotational movement between said projectionand the hole is permitted, and a second relative rotational positionwith respect to the hole in which the relative rotational movement isprevented in one direction while the rotation axis of the gear and therotation axis of said photosensitive drum are substantially aligned.